WORST_CASE(Omega(n^1),O(n^2))
* Step 1: Sum WORST_CASE(Omega(n^1),O(n^2))
    + Considered Problem:
        - Strict TRS:
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            flattensort(t) -> insertionsort(flatten(t))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2} / {0/0,cons/2,false/0,leaf/0
            ,nil/0,node/3,s/1,true/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append,flatten,flattensort,if'insert,insert,insertionsort
            ,leq} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        Sum {left = someStrategy, right = someStrategy}
    + Details:
        ()
** Step 1.a:1: DecreasingLoops WORST_CASE(Omega(n^1),?)
    + Considered Problem:
        - Strict TRS:
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            flattensort(t) -> insertionsort(flatten(t))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2} / {0/0,cons/2,false/0,leaf/0
            ,nil/0,node/3,s/1,true/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append,flatten,flattensort,if'insert,insert,insertionsort
            ,leq} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        DecreasingLoops {bound = AnyLoop, narrow = 10}
    + Details:
        The system has following decreasing Loops:
          flatten(y){y -> node(x,y,z)} =
            flatten(node(x,y,z)) ->^+ append(x,append(flatten(y),flatten(z)))
              = C[flatten(y) = flatten(y){}]

** Step 1.b:1: DependencyPairs WORST_CASE(?,O(n^2))
    + Considered Problem:
        - Strict TRS:
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            flattensort(t) -> insertionsort(flatten(t))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2} / {0/0,cons/2,false/0,leaf/0
            ,nil/0,node/3,s/1,true/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append,flatten,flattensort,if'insert,insert,insertionsort
            ,leq} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        DependencyPairs {dpKind_ = DT}
    + Details:
        We add the following dependency tuples:
        
        Strict DPs
          flatten#(leaf()) -> c_1()
          flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                        ,append#(flatten(t1),flatten(t2))
                                        ,flatten#(t1)
                                        ,flatten#(t2))
          flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
          if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
          if'insert#(true(),x,y,ys) -> c_5()
          insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y))
          insert#(x,nil()) -> c_7()
          insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
          insertionsort#(nil()) -> c_9()
        Weak DPs
          append#(cons(x,xs),l2) -> c_10(append#(xs,l2))
          append#(nil(),l2) -> c_11()
          leq#(0(),y) -> c_12()
          leq#(s(x),0()) -> c_13()
          leq#(s(x),s(y)) -> c_14(leq#(x,y))
        
        and mark the set of starting terms.
** Step 1.b:2: PredecessorEstimation WORST_CASE(?,O(n^2))
    + Considered Problem:
        - Strict DPs:
            flatten#(leaf()) -> c_1()
            flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                          ,append#(flatten(t1),flatten(t2))
                                          ,flatten#(t1)
                                          ,flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            if'insert#(true(),x,y,ys) -> c_5()
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y))
            insert#(x,nil()) -> c_7()
            insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
            insertionsort#(nil()) -> c_9()
        - Weak DPs:
            append#(cons(x,xs),l2) -> c_10(append#(xs,l2))
            append#(nil(),l2) -> c_11()
            leq#(0(),y) -> c_12()
            leq#(s(x),0()) -> c_13()
            leq#(s(x),s(y)) -> c_14(leq#(x,y))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            flattensort(t) -> insertionsort(flatten(t))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/4,c_3/2,c_4/1,c_5/0,c_6/2,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        PredecessorEstimation {onSelection = all simple predecessor estimation selector}
    + Details:
        We estimate the number of application of
          {1,5,7,9}
        by application of
          Pre({1,5,7,9}) = {2,3,4,6,8}.
        Here rules are labelled as follows:
          1: flatten#(leaf()) -> c_1()
          2: flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                           ,append#(flatten(t1),flatten(t2))
                                           ,flatten#(t1)
                                           ,flatten#(t2))
          3: flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
          4: if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
          5: if'insert#(true(),x,y,ys) -> c_5()
          6: insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y))
          7: insert#(x,nil()) -> c_7()
          8: insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
          9: insertionsort#(nil()) -> c_9()
          10: append#(cons(x,xs),l2) -> c_10(append#(xs,l2))
          11: append#(nil(),l2) -> c_11()
          12: leq#(0(),y) -> c_12()
          13: leq#(s(x),0()) -> c_13()
          14: leq#(s(x),s(y)) -> c_14(leq#(x,y))
** Step 1.b:3: RemoveWeakSuffixes WORST_CASE(?,O(n^2))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                          ,append#(flatten(t1),flatten(t2))
                                          ,flatten#(t1)
                                          ,flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y))
            insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
        - Weak DPs:
            append#(cons(x,xs),l2) -> c_10(append#(xs,l2))
            append#(nil(),l2) -> c_11()
            flatten#(leaf()) -> c_1()
            if'insert#(true(),x,y,ys) -> c_5()
            insert#(x,nil()) -> c_7()
            insertionsort#(nil()) -> c_9()
            leq#(0(),y) -> c_12()
            leq#(s(x),0()) -> c_13()
            leq#(s(x),s(y)) -> c_14(leq#(x,y))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            flattensort(t) -> insertionsort(flatten(t))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/4,c_3/2,c_4/1,c_5/0,c_6/2,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        RemoveWeakSuffixes
    + Details:
        Consider the dependency graph
          1:S:flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                            ,append#(flatten(t1),flatten(t2))
                                            ,flatten#(t1)
                                            ,flatten#(t2))
             -->_2 append#(cons(x,xs),l2) -> c_10(append#(xs,l2)):6
             -->_1 append#(cons(x,xs),l2) -> c_10(append#(xs,l2)):6
             -->_4 flatten#(leaf()) -> c_1():8
             -->_3 flatten#(leaf()) -> c_1():8
             -->_2 append#(nil(),l2) -> c_11():7
             -->_1 append#(nil(),l2) -> c_11():7
             -->_4 flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                                 ,append#(flatten(t1),flatten(t2))
                                                 ,flatten#(t1)
                                                 ,flatten#(t2)):1
             -->_3 flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                                 ,append#(flatten(t1),flatten(t2))
                                                 ,flatten#(t1)
                                                 ,flatten#(t2)):1
          
          2:S:flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
             -->_1 insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs)):5
             -->_1 insertionsort#(nil()) -> c_9():11
             -->_2 flatten#(leaf()) -> c_1():8
             -->_2 flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                                 ,append#(flatten(t1),flatten(t2))
                                                 ,flatten#(t1)
                                                 ,flatten#(t2)):1
          
          3:S:if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
             -->_1 insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y)):4
             -->_1 insert#(x,nil()) -> c_7():10
          
          4:S:insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y))
             -->_2 leq#(s(x),s(y)) -> c_14(leq#(x,y)):14
             -->_2 leq#(s(x),0()) -> c_13():13
             -->_2 leq#(0(),y) -> c_12():12
             -->_1 if'insert#(true(),x,y,ys) -> c_5():9
             -->_1 if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys)):3
          
          5:S:insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
             -->_2 insertionsort#(nil()) -> c_9():11
             -->_1 insert#(x,nil()) -> c_7():10
             -->_2 insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs)):5
             -->_1 insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y)):4
          
          6:W:append#(cons(x,xs),l2) -> c_10(append#(xs,l2))
             -->_1 append#(nil(),l2) -> c_11():7
             -->_1 append#(cons(x,xs),l2) -> c_10(append#(xs,l2)):6
          
          7:W:append#(nil(),l2) -> c_11()
             
          
          8:W:flatten#(leaf()) -> c_1()
             
          
          9:W:if'insert#(true(),x,y,ys) -> c_5()
             
          
          10:W:insert#(x,nil()) -> c_7()
             
          
          11:W:insertionsort#(nil()) -> c_9()
             
          
          12:W:leq#(0(),y) -> c_12()
             
          
          13:W:leq#(s(x),0()) -> c_13()
             
          
          14:W:leq#(s(x),s(y)) -> c_14(leq#(x,y))
             -->_1 leq#(s(x),s(y)) -> c_14(leq#(x,y)):14
             -->_1 leq#(s(x),0()) -> c_13():13
             -->_1 leq#(0(),y) -> c_12():12
          
        The following weak DPs constitute a sub-graph of the DG that is closed under successors. The DPs are removed.
          9: if'insert#(true(),x,y,ys) -> c_5()
          14: leq#(s(x),s(y)) -> c_14(leq#(x,y))
          12: leq#(0(),y) -> c_12()
          13: leq#(s(x),0()) -> c_13()
          10: insert#(x,nil()) -> c_7()
          11: insertionsort#(nil()) -> c_9()
          8: flatten#(leaf()) -> c_1()
          6: append#(cons(x,xs),l2) -> c_10(append#(xs,l2))
          7: append#(nil(),l2) -> c_11()
** Step 1.b:4: SimplifyRHS WORST_CASE(?,O(n^2))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                          ,append#(flatten(t1),flatten(t2))
                                          ,flatten#(t1)
                                          ,flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y))
            insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            flattensort(t) -> insertionsort(flatten(t))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/4,c_3/2,c_4/1,c_5/0,c_6/2,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        SimplifyRHS
    + Details:
        Consider the dependency graph
          1:S:flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                            ,append#(flatten(t1),flatten(t2))
                                            ,flatten#(t1)
                                            ,flatten#(t2))
             -->_4 flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                                 ,append#(flatten(t1),flatten(t2))
                                                 ,flatten#(t1)
                                                 ,flatten#(t2)):1
             -->_3 flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                                 ,append#(flatten(t1),flatten(t2))
                                                 ,flatten#(t1)
                                                 ,flatten#(t2)):1
          
          2:S:flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
             -->_1 insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs)):5
             -->_2 flatten#(node(l,t1,t2)) -> c_2(append#(l,append(flatten(t1),flatten(t2)))
                                                 ,append#(flatten(t1),flatten(t2))
                                                 ,flatten#(t1)
                                                 ,flatten#(t2)):1
          
          3:S:if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
             -->_1 insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y)):4
          
          4:S:insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y))
             -->_1 if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys)):3
          
          5:S:insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
             -->_2 insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs)):5
             -->_1 insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys),leq#(x,y)):4
          
        Due to missing edges in the depndency graph, the right-hand sides of following rules could be simplified:
          flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
          insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
** Step 1.b:5: UsableRules WORST_CASE(?,O(n^2))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
            insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            flattensort(t) -> insertionsort(flatten(t))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        UsableRules
    + Details:
        We replace rewrite rules by usable rules:
          append(cons(x,xs),l2) -> cons(x,append(xs,l2))
          append(nil(),l2) -> l2
          flatten(leaf()) -> nil()
          flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
          if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
          if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
          insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
          insert(x,nil()) -> cons(x,nil())
          insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
          insertionsort(nil()) -> nil()
          leq(0(),y) -> true()
          leq(s(x),0()) -> false()
          leq(s(x),s(y)) -> leq(x,y)
          flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
          flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
          if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
          insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
          insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
** Step 1.b:6: DecomposeDG WORST_CASE(?,O(n^2))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
            insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        DecomposeDG {onSelection = all below first cut in WDG, onUpper = Nothing, onLower = Nothing}
    + Details:
        We decompose the input problem according to the dependency graph into the upper component
          flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
          flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
          insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
        and a lower component
          if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
          insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
        Further, following extension rules are added to the lower component.
          flatten#(node(l,t1,t2)) -> flatten#(t1)
          flatten#(node(l,t1,t2)) -> flatten#(t2)
          flattensort#(t) -> flatten#(t)
          flattensort#(t) -> insertionsort#(flatten(t))
          insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs))
          insertionsort#(cons(x,xs)) -> insertionsort#(xs)
*** Step 1.b:6.a:1: SimplifyRHS WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        SimplifyRHS
    + Details:
        Consider the dependency graph
          1:S:flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
             -->_2 flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2)):1
             -->_1 flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2)):1
          
          2:S:flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
             -->_1 insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs)):3
             -->_2 flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2)):1
          
          3:S:insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs))
             -->_2 insertionsort#(cons(x,xs)) -> c_8(insert#(x,insertionsort(xs)),insertionsort#(xs)):3
          
        Due to missing edges in the depndency graph, the right-hand sides of following rules could be simplified:
          insertionsort#(cons(x,xs)) -> c_8(insertionsort#(xs))
*** Step 1.b:6.a:2: UsableRules WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            insertionsort#(cons(x,xs)) -> c_8(insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/1,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        UsableRules
    + Details:
        We replace rewrite rules by usable rules:
          append(cons(x,xs),l2) -> cons(x,append(xs,l2))
          append(nil(),l2) -> l2
          flatten(leaf()) -> nil()
          flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
          flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
          flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
          insertionsort#(cons(x,xs)) -> c_8(insertionsort#(xs))
*** Step 1.b:6.a:3: WeightGap WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            insertionsort#(cons(x,xs)) -> c_8(insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/1,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        WeightGap {wgDimension = 1, wgDegree = 1, wgKind = Algebraic, wgUArgs = UArgs, wgOn = WgOnAny}
    + Details:
        The weightgap principle applies using the following constant growth matrix-interpretation:
          We apply a matrix interpretation of kind constructor based matrix interpretation:
          The following argument positions are considered usable:
            uargs(append) = {1,2},
            uargs(cons) = {2},
            uargs(insertionsort#) = {1},
            uargs(c_2) = {1,2},
            uargs(c_3) = {1,2},
            uargs(c_8) = {1}
          
          Following symbols are considered usable:
            all
          TcT has computed the following interpretation:
                         p(0) = [0]                           
                    p(append) = [1] x1 + [1] x2 + [0]         
                      p(cons) = [1] x1 + [1] x2 + [0]         
                     p(false) = [0]                           
                   p(flatten) = [1] x1 + [0]                  
               p(flattensort) = [0]                           
                 p(if'insert) = [0]                           
                    p(insert) = [0]                           
             p(insertionsort) = [0]                           
                      p(leaf) = [0]                           
                       p(leq) = [0]                           
                       p(nil) = [0]                           
                      p(node) = [1] x1 + [1] x2 + [1] x3 + [0]
                         p(s) = [1] x1 + [0]                  
                      p(true) = [0]                           
                   p(append#) = [0]                           
                  p(flatten#) = [5] x1 + [0]                  
              p(flattensort#) = [6] x1 + [9]                  
                p(if'insert#) = [0]                           
                   p(insert#) = [0]                           
            p(insertionsort#) = [1] x1 + [0]                  
                      p(leq#) = [0]                           
                       p(c_1) = [0]                           
                       p(c_2) = [1] x1 + [1] x2 + [0]         
                       p(c_3) = [1] x1 + [1] x2 + [0]         
                       p(c_4) = [0]                           
                       p(c_5) = [0]                           
                       p(c_6) = [0]                           
                       p(c_7) = [0]                           
                       p(c_8) = [1] x1 + [0]                  
                       p(c_9) = [0]                           
                      p(c_10) = [0]                           
                      p(c_11) = [0]                           
                      p(c_12) = [0]                           
                      p(c_13) = [0]                           
                      p(c_14) = [0]                           
          
          Following rules are strictly oriented:
          flattensort#(t) = [6] t + [9]                                
                          > [6] t + [0]                                
                          = c_3(insertionsort#(flatten(t)),flatten#(t))
          
          
          Following rules are (at-least) weakly oriented:
             flatten#(node(l,t1,t2)) =  [5] l + [5] t1 + [5] t2 + [0]            
                                     >= [5] t1 + [5] t2 + [0]                    
                                     =  c_2(flatten#(t1),flatten#(t2))           
          
          insertionsort#(cons(x,xs)) =  [1] x + [1] xs + [0]                     
                                     >= [1] xs + [0]                             
                                     =  c_8(insertionsort#(xs))                  
          
               append(cons(x,xs),l2) =  [1] l2 + [1] x + [1] xs + [0]            
                                     >= [1] l2 + [1] x + [1] xs + [0]            
                                     =  cons(x,append(xs,l2))                    
          
                    append(nil(),l2) =  [1] l2 + [0]                             
                                     >= [1] l2 + [0]                             
                                     =  l2                                       
          
                     flatten(leaf()) =  [0]                                      
                                     >= [0]                                      
                                     =  nil()                                    
          
              flatten(node(l,t1,t2)) =  [1] l + [1] t1 + [1] t2 + [0]            
                                     >= [1] l + [1] t1 + [1] t2 + [0]            
                                     =  append(l,append(flatten(t1),flatten(t2)))
          
        Further, it can be verified that all rules not oriented are covered by the weightgap condition.
*** Step 1.b:6.a:4: WeightGap WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
            insertionsort#(cons(x,xs)) -> c_8(insertionsort#(xs))
        - Weak DPs:
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/1,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        WeightGap {wgDimension = 1, wgDegree = 1, wgKind = Algebraic, wgUArgs = UArgs, wgOn = WgOnAny}
    + Details:
        The weightgap principle applies using the following constant growth matrix-interpretation:
          We apply a matrix interpretation of kind constructor based matrix interpretation:
          The following argument positions are considered usable:
            uargs(append) = {1,2},
            uargs(cons) = {2},
            uargs(insertionsort#) = {1},
            uargs(c_2) = {1,2},
            uargs(c_3) = {1,2},
            uargs(c_8) = {1}
          
          Following symbols are considered usable:
            all
          TcT has computed the following interpretation:
                         p(0) = [0]                           
                    p(append) = [1] x1 + [1] x2 + [0]         
                      p(cons) = [1] x1 + [1] x2 + [15]        
                     p(false) = [0]                           
                   p(flatten) = [1] x1 + [0]                  
               p(flattensort) = [0]                           
                 p(if'insert) = [0]                           
                    p(insert) = [0]                           
             p(insertionsort) = [0]                           
                      p(leaf) = [0]                           
                       p(leq) = [0]                           
                       p(nil) = [0]                           
                      p(node) = [1] x1 + [1] x2 + [1] x3 + [0]
                         p(s) = [1] x1 + [0]                  
                      p(true) = [0]                           
                   p(append#) = [0]                           
                  p(flatten#) = [5] x1 + [0]                  
              p(flattensort#) = [6] x1 + [0]                  
                p(if'insert#) = [0]                           
                   p(insert#) = [0]                           
            p(insertionsort#) = [1] x1 + [0]                  
                      p(leq#) = [0]                           
                       p(c_1) = [0]                           
                       p(c_2) = [1] x1 + [1] x2 + [0]         
                       p(c_3) = [1] x1 + [1] x2 + [0]         
                       p(c_4) = [0]                           
                       p(c_5) = [0]                           
                       p(c_6) = [0]                           
                       p(c_7) = [0]                           
                       p(c_8) = [1] x1 + [0]                  
                       p(c_9) = [0]                           
                      p(c_10) = [0]                           
                      p(c_11) = [0]                           
                      p(c_12) = [0]                           
                      p(c_13) = [0]                           
                      p(c_14) = [0]                           
          
          Following rules are strictly oriented:
          insertionsort#(cons(x,xs)) = [1] x + [1] xs + [15]  
                                     > [1] xs + [0]           
                                     = c_8(insertionsort#(xs))
          
          
          Following rules are (at-least) weakly oriented:
          flatten#(node(l,t1,t2)) =  [5] l + [5] t1 + [5] t2 + [0]              
                                  >= [5] t1 + [5] t2 + [0]                      
                                  =  c_2(flatten#(t1),flatten#(t2))             
          
                  flattensort#(t) =  [6] t + [0]                                
                                  >= [6] t + [0]                                
                                  =  c_3(insertionsort#(flatten(t)),flatten#(t))
          
            append(cons(x,xs),l2) =  [1] l2 + [1] x + [1] xs + [15]             
                                  >= [1] l2 + [1] x + [1] xs + [15]             
                                  =  cons(x,append(xs,l2))                      
          
                 append(nil(),l2) =  [1] l2 + [0]                               
                                  >= [1] l2 + [0]                               
                                  =  l2                                         
          
                  flatten(leaf()) =  [0]                                        
                                  >= [0]                                        
                                  =  nil()                                      
          
           flatten(node(l,t1,t2)) =  [1] l + [1] t1 + [1] t2 + [0]              
                                  >= [1] l + [1] t1 + [1] t2 + [0]              
                                  =  append(l,append(flatten(t1),flatten(t2)))  
          
        Further, it can be verified that all rules not oriented are covered by the weightgap condition.
*** Step 1.b:6.a:5: WeightGap WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
        - Weak DPs:
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            insertionsort#(cons(x,xs)) -> c_8(insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/1,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        WeightGap {wgDimension = 1, wgDegree = 1, wgKind = Algebraic, wgUArgs = UArgs, wgOn = WgOnAny}
    + Details:
        The weightgap principle applies using the following constant growth matrix-interpretation:
          We apply a matrix interpretation of kind constructor based matrix interpretation:
          The following argument positions are considered usable:
            uargs(append) = {1,2},
            uargs(cons) = {2},
            uargs(insertionsort#) = {1},
            uargs(c_2) = {1,2},
            uargs(c_3) = {1,2},
            uargs(c_8) = {1}
          
          Following symbols are considered usable:
            all
          TcT has computed the following interpretation:
                         p(0) = [0]                                    
                    p(append) = [1] x1 + [1] x2 + [1]                  
                      p(cons) = [1] x1 + [1] x2 + [2]                  
                     p(false) = [0]                                    
                   p(flatten) = [3] x1 + [5]                           
               p(flattensort) = [0]                                    
                 p(if'insert) = [0]                                    
                    p(insert) = [0]                                    
             p(insertionsort) = [0]                                    
                      p(leaf) = [2]                                    
                       p(leq) = [1] x2 + [8]                           
                       p(nil) = [0]                                    
                      p(node) = [1] x1 + [1] x2 + [1] x3 + [4]         
                         p(s) = [2]                                    
                      p(true) = [1]                                    
                   p(append#) = [1] x2 + [2]                           
                  p(flatten#) = [4] x1 + [0]                           
              p(flattensort#) = [9] x1 + [8]                           
                p(if'insert#) = [1] x1 + [1] x2 + [1] x3 + [8] x4 + [1]
                   p(insert#) = [1] x1 + [1] x2 + [1]                  
            p(insertionsort#) = [1] x1 + [2]                           
                      p(leq#) = [1] x1 + [0]                           
                       p(c_1) = [0]                                    
                       p(c_2) = [1] x1 + [1] x2 + [12]                 
                       p(c_3) = [1] x1 + [1] x2 + [1]                  
                       p(c_4) = [1] x1 + [1]                           
                       p(c_5) = [1]                                    
                       p(c_6) = [1]                                    
                       p(c_7) = [0]                                    
                       p(c_8) = [1] x1 + [0]                           
                       p(c_9) = [2]                                    
                      p(c_10) = [1] x1 + [8]                           
                      p(c_11) = [1]                                    
                      p(c_12) = [0]                                    
                      p(c_13) = [1]                                    
                      p(c_14) = [8] x1 + [2]                           
          
          Following rules are strictly oriented:
          flatten#(node(l,t1,t2)) = [4] l + [4] t1 + [4] t2 + [16]
                                  > [4] t1 + [4] t2 + [12]        
                                  = c_2(flatten#(t1),flatten#(t2))
          
          
          Following rules are (at-least) weakly oriented:
                     flattensort#(t) =  [9] t + [8]                                
                                     >= [7] t + [8]                                
                                     =  c_3(insertionsort#(flatten(t)),flatten#(t))
          
          insertionsort#(cons(x,xs)) =  [1] x + [1] xs + [4]                       
                                     >= [1] xs + [2]                               
                                     =  c_8(insertionsort#(xs))                    
          
               append(cons(x,xs),l2) =  [1] l2 + [1] x + [1] xs + [3]              
                                     >= [1] l2 + [1] x + [1] xs + [3]              
                                     =  cons(x,append(xs,l2))                      
          
                    append(nil(),l2) =  [1] l2 + [1]                               
                                     >= [1] l2 + [0]                               
                                     =  l2                                         
          
                     flatten(leaf()) =  [11]                                       
                                     >= [0]                                        
                                     =  nil()                                      
          
              flatten(node(l,t1,t2)) =  [3] l + [3] t1 + [3] t2 + [17]             
                                     >= [1] l + [3] t1 + [3] t2 + [12]             
                                     =  append(l,append(flatten(t1),flatten(t2)))  
          
        Further, it can be verified that all rules not oriented are covered by the weightgap condition.
*** Step 1.b:6.a:6: EmptyProcessor WORST_CASE(?,O(1))
    + Considered Problem:
        - Weak DPs:
            flatten#(node(l,t1,t2)) -> c_2(flatten#(t1),flatten#(t2))
            flattensort#(t) -> c_3(insertionsort#(flatten(t)),flatten#(t))
            insertionsort#(cons(x,xs)) -> c_8(insertionsort#(xs))
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/1,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        EmptyProcessor
    + Details:
        The problem is already closed. The intended complexity is O(1).

*** Step 1.b:6.b:1: RemoveWeakSuffixes WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
        - Weak DPs:
            flatten#(node(l,t1,t2)) -> flatten#(t1)
            flatten#(node(l,t1,t2)) -> flatten#(t2)
            flattensort#(t) -> flatten#(t)
            flattensort#(t) -> insertionsort#(flatten(t))
            insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs))
            insertionsort#(cons(x,xs)) -> insertionsort#(xs)
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        RemoveWeakSuffixes
    + Details:
        Consider the dependency graph
          1:S:if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
             -->_1 insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys)):2
          
          2:S:insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
             -->_1 if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys)):1
          
          3:W:flatten#(node(l,t1,t2)) -> flatten#(t1)
             -->_1 flatten#(node(l,t1,t2)) -> flatten#(t2):4
             -->_1 flatten#(node(l,t1,t2)) -> flatten#(t1):3
          
          4:W:flatten#(node(l,t1,t2)) -> flatten#(t2)
             -->_1 flatten#(node(l,t1,t2)) -> flatten#(t2):4
             -->_1 flatten#(node(l,t1,t2)) -> flatten#(t1):3
          
          5:W:flattensort#(t) -> flatten#(t)
             -->_1 flatten#(node(l,t1,t2)) -> flatten#(t2):4
             -->_1 flatten#(node(l,t1,t2)) -> flatten#(t1):3
          
          6:W:flattensort#(t) -> insertionsort#(flatten(t))
             -->_1 insertionsort#(cons(x,xs)) -> insertionsort#(xs):8
             -->_1 insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs)):7
          
          7:W:insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs))
             -->_1 insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys)):2
          
          8:W:insertionsort#(cons(x,xs)) -> insertionsort#(xs)
             -->_1 insertionsort#(cons(x,xs)) -> insertionsort#(xs):8
             -->_1 insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs)):7
          
        The following weak DPs constitute a sub-graph of the DG that is closed under successors. The DPs are removed.
          5: flattensort#(t) -> flatten#(t)
          3: flatten#(node(l,t1,t2)) -> flatten#(t1)
          4: flatten#(node(l,t1,t2)) -> flatten#(t2)
*** Step 1.b:6.b:2: WeightGap WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
        - Weak DPs:
            flattensort#(t) -> insertionsort#(flatten(t))
            insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs))
            insertionsort#(cons(x,xs)) -> insertionsort#(xs)
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        WeightGap {wgDimension = 1, wgDegree = 1, wgKind = Algebraic, wgUArgs = UArgs, wgOn = WgOnAny}
    + Details:
        The weightgap principle applies using the following constant growth matrix-interpretation:
          We apply a matrix interpretation of kind constructor based matrix interpretation:
          The following argument positions are considered usable:
            uargs(append) = {1,2},
            uargs(cons) = {2},
            uargs(if'insert) = {1},
            uargs(insert) = {2},
            uargs(if'insert#) = {1},
            uargs(insert#) = {2},
            uargs(insertionsort#) = {1},
            uargs(c_4) = {1},
            uargs(c_6) = {1}
          
          Following symbols are considered usable:
            all
          TcT has computed the following interpretation:
                         p(0) = [0]                           
                    p(append) = [1] x1 + [1] x2 + [0]         
                      p(cons) = [1] x2 + [2]                  
                     p(false) = [0]                           
                   p(flatten) = [4] x1 + [0]                  
               p(flattensort) = [4] x1 + [1]                  
                 p(if'insert) = [1] x1 + [1] x4 + [4]         
                    p(insert) = [1] x2 + [2]                  
             p(insertionsort) = [1] x1 + [3]                  
                      p(leaf) = [2]                           
                       p(leq) = [0]                           
                       p(nil) = [1]                           
                      p(node) = [1] x1 + [1] x2 + [1] x3 + [0]
                         p(s) = [1] x1 + [0]                  
                      p(true) = [0]                           
                   p(append#) = [2] x2 + [0]                  
                  p(flatten#) = [1] x1 + [2]                  
              p(flattensort#) = [7] x1 + [1]                  
                p(if'insert#) = [1] x1 + [1] x4 + [5]         
                   p(insert#) = [1] x2 + [0]                  
            p(insertionsort#) = [1] x1 + [1]                  
                      p(leq#) = [0]                           
                       p(c_1) = [0]                           
                       p(c_2) = [0]                           
                       p(c_3) = [0]                           
                       p(c_4) = [1] x1 + [0]                  
                       p(c_5) = [0]                           
                       p(c_6) = [1] x1 + [0]                  
                       p(c_7) = [0]                           
                       p(c_8) = [0]                           
                       p(c_9) = [0]                           
                      p(c_10) = [0]                           
                      p(c_11) = [0]                           
                      p(c_12) = [0]                           
                      p(c_13) = [1]                           
                      p(c_14) = [0]                           
          
          Following rules are strictly oriented:
          if'insert#(false(),x,y,ys) = [1] ys + [5]      
                                     > [1] ys + [0]      
                                     = c_4(insert#(x,ys))
          
          
          Following rules are (at-least) weakly oriented:
                     flattensort#(t) =  [7] t + [1]                              
                                     >= [4] t + [1]                              
                                     =  insertionsort#(flatten(t))               
          
               insert#(x,cons(y,ys)) =  [1] ys + [2]                             
                                     >= [1] ys + [5]                             
                                     =  c_6(if'insert#(leq(x,y),x,y,ys))         
          
          insertionsort#(cons(x,xs)) =  [1] xs + [3]                             
                                     >= [1] xs + [3]                             
                                     =  insert#(x,insertionsort(xs))             
          
          insertionsort#(cons(x,xs)) =  [1] xs + [3]                             
                                     >= [1] xs + [1]                             
                                     =  insertionsort#(xs)                       
          
               append(cons(x,xs),l2) =  [1] l2 + [1] xs + [2]                    
                                     >= [1] l2 + [1] xs + [2]                    
                                     =  cons(x,append(xs,l2))                    
          
                    append(nil(),l2) =  [1] l2 + [1]                             
                                     >= [1] l2 + [0]                             
                                     =  l2                                       
          
                     flatten(leaf()) =  [8]                                      
                                     >= [1]                                      
                                     =  nil()                                    
          
              flatten(node(l,t1,t2)) =  [4] l + [4] t1 + [4] t2 + [0]            
                                     >= [1] l + [4] t1 + [4] t2 + [0]            
                                     =  append(l,append(flatten(t1),flatten(t2)))
          
           if'insert(false(),x,y,ys) =  [1] ys + [4]                             
                                     >= [1] ys + [4]                             
                                     =  cons(y,insert(x,ys))                     
          
            if'insert(true(),x,y,ys) =  [1] ys + [4]                             
                                     >= [1] ys + [4]                             
                                     =  cons(x,cons(y,ys))                       
          
                insert(x,cons(y,ys)) =  [1] ys + [4]                             
                                     >= [1] ys + [4]                             
                                     =  if'insert(leq(x,y),x,y,ys)               
          
                     insert(x,nil()) =  [3]                                      
                                     >= [3]                                      
                                     =  cons(x,nil())                            
          
           insertionsort(cons(x,xs)) =  [1] xs + [5]                             
                                     >= [1] xs + [5]                             
                                     =  insert(x,insertionsort(xs))              
          
                insertionsort(nil()) =  [4]                                      
                                     >= [1]                                      
                                     =  nil()                                    
          
                          leq(0(),y) =  [0]                                      
                                     >= [0]                                      
                                     =  true()                                   
          
                       leq(s(x),0()) =  [0]                                      
                                     >= [0]                                      
                                     =  false()                                  
          
                      leq(s(x),s(y)) =  [0]                                      
                                     >= [0]                                      
                                     =  leq(x,y)                                 
          
        Further, it can be verified that all rules not oriented are covered by the weightgap condition.
*** Step 1.b:6.b:3: WeightGap WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict DPs:
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
        - Weak DPs:
            flattensort#(t) -> insertionsort#(flatten(t))
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs))
            insertionsort#(cons(x,xs)) -> insertionsort#(xs)
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        WeightGap {wgDimension = 1, wgDegree = 1, wgKind = Algebraic, wgUArgs = UArgs, wgOn = WgOnAny}
    + Details:
        The weightgap principle applies using the following constant growth matrix-interpretation:
          We apply a matrix interpretation of kind constructor based matrix interpretation:
          The following argument positions are considered usable:
            uargs(append) = {1,2},
            uargs(cons) = {2},
            uargs(if'insert) = {1},
            uargs(insert) = {2},
            uargs(if'insert#) = {1},
            uargs(insert#) = {2},
            uargs(insertionsort#) = {1},
            uargs(c_4) = {1},
            uargs(c_6) = {1}
          
          Following symbols are considered usable:
            all
          TcT has computed the following interpretation:
                         p(0) = [0]                           
                    p(append) = [1] x1 + [1] x2 + [1]         
                      p(cons) = [1] x2 + [4]                  
                     p(false) = [4]                           
                   p(flatten) = [1] x1 + [1]                  
               p(flattensort) = [1] x1 + [0]                  
                 p(if'insert) = [1] x1 + [1] x4 + [4]         
                    p(insert) = [1] x2 + [4]                  
             p(insertionsort) = [1] x1 + [2]                  
                      p(leaf) = [4]                           
                       p(leq) = [4]                           
                       p(nil) = [4]                           
                      p(node) = [1] x1 + [1] x2 + [1] x3 + [4]
                         p(s) = [1]                           
                      p(true) = [4]                           
                   p(append#) = [1] x1 + [4] x2 + [1]         
                  p(flatten#) = [2] x1 + [1]                  
              p(flattensort#) = [4] x1 + [7]                  
                p(if'insert#) = [1] x1 + [1] x4 + [2]         
                   p(insert#) = [1] x2 + [5]                  
            p(insertionsort#) = [1] x1 + [6]                  
                      p(leq#) = [0]                           
                       p(c_1) = [0]                           
                       p(c_2) = [4] x1 + [0]                  
                       p(c_3) = [1] x1 + [4] x2 + [1]         
                       p(c_4) = [1] x1 + [1]                  
                       p(c_5) = [0]                           
                       p(c_6) = [1] x1 + [2]                  
                       p(c_7) = [1]                           
                       p(c_8) = [2] x1 + [1] x2 + [0]         
                       p(c_9) = [1]                           
                      p(c_10) = [2] x1 + [0]                  
                      p(c_11) = [2]                           
                      p(c_12) = [1]                           
                      p(c_13) = [0]                           
                      p(c_14) = [4] x1 + [1]                  
          
          Following rules are strictly oriented:
          insert#(x,cons(y,ys)) = [1] ys + [9]                    
                                > [1] ys + [8]                    
                                = c_6(if'insert#(leq(x,y),x,y,ys))
          
          
          Following rules are (at-least) weakly oriented:
                     flattensort#(t) =  [4] t + [7]                              
                                     >= [1] t + [7]                              
                                     =  insertionsort#(flatten(t))               
          
          if'insert#(false(),x,y,ys) =  [1] ys + [6]                             
                                     >= [1] ys + [6]                             
                                     =  c_4(insert#(x,ys))                       
          
          insertionsort#(cons(x,xs)) =  [1] xs + [10]                            
                                     >= [1] xs + [7]                             
                                     =  insert#(x,insertionsort(xs))             
          
          insertionsort#(cons(x,xs)) =  [1] xs + [10]                            
                                     >= [1] xs + [6]                             
                                     =  insertionsort#(xs)                       
          
               append(cons(x,xs),l2) =  [1] l2 + [1] xs + [5]                    
                                     >= [1] l2 + [1] xs + [5]                    
                                     =  cons(x,append(xs,l2))                    
          
                    append(nil(),l2) =  [1] l2 + [5]                             
                                     >= [1] l2 + [0]                             
                                     =  l2                                       
          
                     flatten(leaf()) =  [5]                                      
                                     >= [4]                                      
                                     =  nil()                                    
          
              flatten(node(l,t1,t2)) =  [1] l + [1] t1 + [1] t2 + [5]            
                                     >= [1] l + [1] t1 + [1] t2 + [4]            
                                     =  append(l,append(flatten(t1),flatten(t2)))
          
           if'insert(false(),x,y,ys) =  [1] ys + [8]                             
                                     >= [1] ys + [8]                             
                                     =  cons(y,insert(x,ys))                     
          
            if'insert(true(),x,y,ys) =  [1] ys + [8]                             
                                     >= [1] ys + [8]                             
                                     =  cons(x,cons(y,ys))                       
          
                insert(x,cons(y,ys)) =  [1] ys + [8]                             
                                     >= [1] ys + [8]                             
                                     =  if'insert(leq(x,y),x,y,ys)               
          
                     insert(x,nil()) =  [8]                                      
                                     >= [8]                                      
                                     =  cons(x,nil())                            
          
           insertionsort(cons(x,xs)) =  [1] xs + [6]                             
                                     >= [1] xs + [6]                             
                                     =  insert(x,insertionsort(xs))              
          
                insertionsort(nil()) =  [6]                                      
                                     >= [4]                                      
                                     =  nil()                                    
          
                          leq(0(),y) =  [4]                                      
                                     >= [4]                                      
                                     =  true()                                   
          
                       leq(s(x),0()) =  [4]                                      
                                     >= [4]                                      
                                     =  false()                                  
          
                      leq(s(x),s(y)) =  [4]                                      
                                     >= [4]                                      
                                     =  leq(x,y)                                 
          
        Further, it can be verified that all rules not oriented are covered by the weightgap condition.
*** Step 1.b:6.b:4: EmptyProcessor WORST_CASE(?,O(1))
    + Considered Problem:
        - Weak DPs:
            flattensort#(t) -> insertionsort#(flatten(t))
            if'insert#(false(),x,y,ys) -> c_4(insert#(x,ys))
            insert#(x,cons(y,ys)) -> c_6(if'insert#(leq(x,y),x,y,ys))
            insertionsort#(cons(x,xs)) -> insert#(x,insertionsort(xs))
            insertionsort#(cons(x,xs)) -> insertionsort#(xs)
        - Weak TRS:
            append(cons(x,xs),l2) -> cons(x,append(xs,l2))
            append(nil(),l2) -> l2
            flatten(leaf()) -> nil()
            flatten(node(l,t1,t2)) -> append(l,append(flatten(t1),flatten(t2)))
            if'insert(false(),x,y,ys) -> cons(y,insert(x,ys))
            if'insert(true(),x,y,ys) -> cons(x,cons(y,ys))
            insert(x,cons(y,ys)) -> if'insert(leq(x,y),x,y,ys)
            insert(x,nil()) -> cons(x,nil())
            insertionsort(cons(x,xs)) -> insert(x,insertionsort(xs))
            insertionsort(nil()) -> nil()
            leq(0(),y) -> true()
            leq(s(x),0()) -> false()
            leq(s(x),s(y)) -> leq(x,y)
        - Signature:
            {append/2,flatten/1,flattensort/1,if'insert/4,insert/2,insertionsort/1,leq/2,append#/2,flatten#/1
            ,flattensort#/1,if'insert#/4,insert#/2,insertionsort#/1,leq#/2} / {0/0,cons/2,false/0,leaf/0,nil/0,node/3
            ,s/1,true/0,c_1/0,c_2/2,c_3/2,c_4/1,c_5/0,c_6/1,c_7/0,c_8/2,c_9/0,c_10/1,c_11/0,c_12/0,c_13/0,c_14/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {append#,flatten#,flattensort#,if'insert#,insert#
            ,insertionsort#,leq#} and constructors {0,cons,false,leaf,nil,node,s,true}
    + Applied Processor:
        EmptyProcessor
    + Details:
        The problem is already closed. The intended complexity is O(1).

WORST_CASE(Omega(n^1),O(n^2))