MAYBE
* Step 1: DependencyPairs MAYBE
    + Considered Problem:
        - Strict TRS:
            a__U11(X1,X2) -> U11(X1,X2)
            a__U11(tt(),N) -> mark(N)
            a__U21(X1,X2,X3) -> U21(X1,X2,X3)
            a__U21(tt(),M,N) -> s(a__plus(mark(N),mark(M)))
            a__and(X1,X2) -> and(X1,X2)
            a__and(tt(),X) -> mark(X)
            a__isNat(X) -> isNat(X)
            a__isNat(0()) -> tt()
            a__isNat(plus(V1,V2)) -> a__and(a__isNat(V1),isNat(V2))
            a__isNat(s(V1)) -> a__isNat(V1)
            a__plus(N,0()) -> a__U11(a__isNat(N),N)
            a__plus(N,s(M)) -> a__U21(a__and(a__isNat(M),isNat(N)),M,N)
            a__plus(X1,X2) -> plus(X1,X2)
            mark(0()) -> 0()
            mark(U11(X1,X2)) -> a__U11(mark(X1),X2)
            mark(U21(X1,X2,X3)) -> a__U21(mark(X1),X2,X3)
            mark(and(X1,X2)) -> a__and(mark(X1),X2)
            mark(isNat(X)) -> a__isNat(X)
            mark(plus(X1,X2)) -> a__plus(mark(X1),mark(X2))
            mark(s(X)) -> s(mark(X))
            mark(tt()) -> tt()
        - Signature:
            {a__U11/2,a__U21/3,a__and/2,a__isNat/1,a__plus/2,mark/1} / {0/0,U11/2,U21/3,and/2,isNat/1,plus/2,s/1,tt/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {a__U11,a__U21,a__and,a__isNat,a__plus
            ,mark} and constructors {0,U11,U21,and,isNat,plus,s,tt}
    + Applied Processor:
        DependencyPairs {dpKind_ = DT}
    + Details:
        We add the following dependency tuples:
        
        Strict DPs
          a__U11#(X1,X2) -> c_1()
          a__U11#(tt(),N) -> c_2(mark#(N))
          a__U21#(X1,X2,X3) -> c_3()
          a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M))
          a__and#(X1,X2) -> c_5()
          a__and#(tt(),X) -> c_6(mark#(X))
          a__isNat#(X) -> c_7()
          a__isNat#(0()) -> c_8()
          a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1))
          a__isNat#(s(V1)) -> c_10(a__isNat#(V1))
          a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N))
          a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                  ,a__and#(a__isNat(M),isNat(N))
                                  ,a__isNat#(M))
          a__plus#(X1,X2) -> c_13()
          mark#(0()) -> c_14()
          mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1))
          mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1))
          mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1))
          mark#(isNat(X)) -> c_18(a__isNat#(X))
          mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2))
          mark#(s(X)) -> c_20(mark#(X))
          mark#(tt()) -> c_21()
        Weak DPs
          
        
        and mark the set of starting terms.
* Step 2: PredecessorEstimation MAYBE
    + Considered Problem:
        - Strict DPs:
            a__U11#(X1,X2) -> c_1()
            a__U11#(tt(),N) -> c_2(mark#(N))
            a__U21#(X1,X2,X3) -> c_3()
            a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M))
            a__and#(X1,X2) -> c_5()
            a__and#(tt(),X) -> c_6(mark#(X))
            a__isNat#(X) -> c_7()
            a__isNat#(0()) -> c_8()
            a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1))
            a__isNat#(s(V1)) -> c_10(a__isNat#(V1))
            a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N))
            a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                    ,a__and#(a__isNat(M),isNat(N))
                                    ,a__isNat#(M))
            a__plus#(X1,X2) -> c_13()
            mark#(0()) -> c_14()
            mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1))
            mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1))
            mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1))
            mark#(isNat(X)) -> c_18(a__isNat#(X))
            mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2))
            mark#(s(X)) -> c_20(mark#(X))
            mark#(tt()) -> c_21()
        - Weak TRS:
            a__U11(X1,X2) -> U11(X1,X2)
            a__U11(tt(),N) -> mark(N)
            a__U21(X1,X2,X3) -> U21(X1,X2,X3)
            a__U21(tt(),M,N) -> s(a__plus(mark(N),mark(M)))
            a__and(X1,X2) -> and(X1,X2)
            a__and(tt(),X) -> mark(X)
            a__isNat(X) -> isNat(X)
            a__isNat(0()) -> tt()
            a__isNat(plus(V1,V2)) -> a__and(a__isNat(V1),isNat(V2))
            a__isNat(s(V1)) -> a__isNat(V1)
            a__plus(N,0()) -> a__U11(a__isNat(N),N)
            a__plus(N,s(M)) -> a__U21(a__and(a__isNat(M),isNat(N)),M,N)
            a__plus(X1,X2) -> plus(X1,X2)
            mark(0()) -> 0()
            mark(U11(X1,X2)) -> a__U11(mark(X1),X2)
            mark(U21(X1,X2,X3)) -> a__U21(mark(X1),X2,X3)
            mark(and(X1,X2)) -> a__and(mark(X1),X2)
            mark(isNat(X)) -> a__isNat(X)
            mark(plus(X1,X2)) -> a__plus(mark(X1),mark(X2))
            mark(s(X)) -> s(mark(X))
            mark(tt()) -> tt()
        - Signature:
            {a__U11/2,a__U21/3,a__and/2,a__isNat/1,a__plus/2,mark/1,a__U11#/2,a__U21#/3,a__and#/2,a__isNat#/1,a__plus#/2
            ,mark#/1} / {0/0,U11/2,U21/3,and/2,isNat/1,plus/2,s/1,tt/0,c_1/0,c_2/1,c_3/0,c_4/3,c_5/0,c_6/1,c_7/0,c_8/0
            ,c_9/2,c_10/1,c_11/2,c_12/3,c_13/0,c_14/0,c_15/2,c_16/2,c_17/2,c_18/1,c_19/3,c_20/1,c_21/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {a__U11#,a__U21#,a__and#,a__isNat#,a__plus#
            ,mark#} and constructors {0,U11,U21,and,isNat,plus,s,tt}
    + Applied Processor:
        PredecessorEstimation {onSelection = all simple predecessor estimation selector}
    + Details:
        We estimate the number of application of
          {1,3,5,7,8,13,14,21}
        by application of
          Pre({1,3,5,7,8,13,14,21}) = {2,4,6,9,10,11,12,15,16,17,18,19,20}.
        Here rules are labelled as follows:
          1: a__U11#(X1,X2) -> c_1()
          2: a__U11#(tt(),N) -> c_2(mark#(N))
          3: a__U21#(X1,X2,X3) -> c_3()
          4: a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M))
          5: a__and#(X1,X2) -> c_5()
          6: a__and#(tt(),X) -> c_6(mark#(X))
          7: a__isNat#(X) -> c_7()
          8: a__isNat#(0()) -> c_8()
          9: a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1))
          10: a__isNat#(s(V1)) -> c_10(a__isNat#(V1))
          11: a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N))
          12: a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                      ,a__and#(a__isNat(M),isNat(N))
                                      ,a__isNat#(M))
          13: a__plus#(X1,X2) -> c_13()
          14: mark#(0()) -> c_14()
          15: mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1))
          16: mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1))
          17: mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1))
          18: mark#(isNat(X)) -> c_18(a__isNat#(X))
          19: mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2))
          20: mark#(s(X)) -> c_20(mark#(X))
          21: mark#(tt()) -> c_21()
* Step 3: RemoveWeakSuffixes MAYBE
    + Considered Problem:
        - Strict DPs:
            a__U11#(tt(),N) -> c_2(mark#(N))
            a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M))
            a__and#(tt(),X) -> c_6(mark#(X))
            a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1))
            a__isNat#(s(V1)) -> c_10(a__isNat#(V1))
            a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N))
            a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                    ,a__and#(a__isNat(M),isNat(N))
                                    ,a__isNat#(M))
            mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1))
            mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1))
            mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1))
            mark#(isNat(X)) -> c_18(a__isNat#(X))
            mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2))
            mark#(s(X)) -> c_20(mark#(X))
        - Weak DPs:
            a__U11#(X1,X2) -> c_1()
            a__U21#(X1,X2,X3) -> c_3()
            a__and#(X1,X2) -> c_5()
            a__isNat#(X) -> c_7()
            a__isNat#(0()) -> c_8()
            a__plus#(X1,X2) -> c_13()
            mark#(0()) -> c_14()
            mark#(tt()) -> c_21()
        - Weak TRS:
            a__U11(X1,X2) -> U11(X1,X2)
            a__U11(tt(),N) -> mark(N)
            a__U21(X1,X2,X3) -> U21(X1,X2,X3)
            a__U21(tt(),M,N) -> s(a__plus(mark(N),mark(M)))
            a__and(X1,X2) -> and(X1,X2)
            a__and(tt(),X) -> mark(X)
            a__isNat(X) -> isNat(X)
            a__isNat(0()) -> tt()
            a__isNat(plus(V1,V2)) -> a__and(a__isNat(V1),isNat(V2))
            a__isNat(s(V1)) -> a__isNat(V1)
            a__plus(N,0()) -> a__U11(a__isNat(N),N)
            a__plus(N,s(M)) -> a__U21(a__and(a__isNat(M),isNat(N)),M,N)
            a__plus(X1,X2) -> plus(X1,X2)
            mark(0()) -> 0()
            mark(U11(X1,X2)) -> a__U11(mark(X1),X2)
            mark(U21(X1,X2,X3)) -> a__U21(mark(X1),X2,X3)
            mark(and(X1,X2)) -> a__and(mark(X1),X2)
            mark(isNat(X)) -> a__isNat(X)
            mark(plus(X1,X2)) -> a__plus(mark(X1),mark(X2))
            mark(s(X)) -> s(mark(X))
            mark(tt()) -> tt()
        - Signature:
            {a__U11/2,a__U21/3,a__and/2,a__isNat/1,a__plus/2,mark/1,a__U11#/2,a__U21#/3,a__and#/2,a__isNat#/1,a__plus#/2
            ,mark#/1} / {0/0,U11/2,U21/3,and/2,isNat/1,plus/2,s/1,tt/0,c_1/0,c_2/1,c_3/0,c_4/3,c_5/0,c_6/1,c_7/0,c_8/0
            ,c_9/2,c_10/1,c_11/2,c_12/3,c_13/0,c_14/0,c_15/2,c_16/2,c_17/2,c_18/1,c_19/3,c_20/1,c_21/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {a__U11#,a__U21#,a__and#,a__isNat#,a__plus#
            ,mark#} and constructors {0,U11,U21,and,isNat,plus,s,tt}
    + Applied Processor:
        RemoveWeakSuffixes
    + Details:
        Consider the dependency graph
          1:S:a__U11#(tt(),N) -> c_2(mark#(N))
             -->_1 mark#(s(X)) -> c_20(mark#(X)):13
             -->_1 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_1 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_1 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_1 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_1 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_1 mark#(tt()) -> c_21():21
             -->_1 mark#(0()) -> c_14():20
          
          2:S:a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M))
             -->_3 mark#(s(X)) -> c_20(mark#(X)):13
             -->_2 mark#(s(X)) -> c_20(mark#(X)):13
             -->_3 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_2 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_3 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_2 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_3 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_2 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_3 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_2 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_3 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_2 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_1 a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                           ,a__and#(a__isNat(M),isNat(N))
                                           ,a__isNat#(M)):7
             -->_1 a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N)):6
             -->_3 mark#(tt()) -> c_21():21
             -->_2 mark#(tt()) -> c_21():21
             -->_3 mark#(0()) -> c_14():20
             -->_2 mark#(0()) -> c_14():20
             -->_1 a__plus#(X1,X2) -> c_13():19
          
          3:S:a__and#(tt(),X) -> c_6(mark#(X))
             -->_1 mark#(s(X)) -> c_20(mark#(X)):13
             -->_1 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_1 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_1 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_1 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_1 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_1 mark#(tt()) -> c_21():21
             -->_1 mark#(0()) -> c_14():20
          
          4:S:a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1))
             -->_2 a__isNat#(s(V1)) -> c_10(a__isNat#(V1)):5
             -->_2 a__isNat#(0()) -> c_8():18
             -->_2 a__isNat#(X) -> c_7():17
             -->_1 a__and#(X1,X2) -> c_5():16
             -->_2 a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1)):4
             -->_1 a__and#(tt(),X) -> c_6(mark#(X)):3
          
          5:S:a__isNat#(s(V1)) -> c_10(a__isNat#(V1))
             -->_1 a__isNat#(0()) -> c_8():18
             -->_1 a__isNat#(X) -> c_7():17
             -->_1 a__isNat#(s(V1)) -> c_10(a__isNat#(V1)):5
             -->_1 a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1)):4
          
          6:S:a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N))
             -->_2 a__isNat#(0()) -> c_8():18
             -->_2 a__isNat#(X) -> c_7():17
             -->_1 a__U11#(X1,X2) -> c_1():14
             -->_2 a__isNat#(s(V1)) -> c_10(a__isNat#(V1)):5
             -->_2 a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1)):4
             -->_1 a__U11#(tt(),N) -> c_2(mark#(N)):1
          
          7:S:a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                      ,a__and#(a__isNat(M),isNat(N))
                                      ,a__isNat#(M))
             -->_3 a__isNat#(0()) -> c_8():18
             -->_3 a__isNat#(X) -> c_7():17
             -->_2 a__and#(X1,X2) -> c_5():16
             -->_1 a__U21#(X1,X2,X3) -> c_3():15
             -->_3 a__isNat#(s(V1)) -> c_10(a__isNat#(V1)):5
             -->_3 a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1)):4
             -->_2 a__and#(tt(),X) -> c_6(mark#(X)):3
             -->_1 a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M)):2
          
          8:S:mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1))
             -->_2 mark#(s(X)) -> c_20(mark#(X)):13
             -->_2 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_2 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_2 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_2 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_2 mark#(tt()) -> c_21():21
             -->_2 mark#(0()) -> c_14():20
             -->_1 a__U11#(X1,X2) -> c_1():14
             -->_2 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_1 a__U11#(tt(),N) -> c_2(mark#(N)):1
          
          9:S:mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1))
             -->_2 mark#(s(X)) -> c_20(mark#(X)):13
             -->_2 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_2 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_2 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_2 mark#(tt()) -> c_21():21
             -->_2 mark#(0()) -> c_14():20
             -->_1 a__U21#(X1,X2,X3) -> c_3():15
             -->_2 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_2 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_1 a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M)):2
          
          10:S:mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1))
             -->_2 mark#(s(X)) -> c_20(mark#(X)):13
             -->_2 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_2 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_2 mark#(tt()) -> c_21():21
             -->_2 mark#(0()) -> c_14():20
             -->_1 a__and#(X1,X2) -> c_5():16
             -->_2 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_2 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_2 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_1 a__and#(tt(),X) -> c_6(mark#(X)):3
          
          11:S:mark#(isNat(X)) -> c_18(a__isNat#(X))
             -->_1 a__isNat#(0()) -> c_8():18
             -->_1 a__isNat#(X) -> c_7():17
             -->_1 a__isNat#(s(V1)) -> c_10(a__isNat#(V1)):5
             -->_1 a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1)):4
          
          12:S:mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2))
             -->_3 mark#(s(X)) -> c_20(mark#(X)):13
             -->_2 mark#(s(X)) -> c_20(mark#(X)):13
             -->_3 mark#(tt()) -> c_21():21
             -->_2 mark#(tt()) -> c_21():21
             -->_3 mark#(0()) -> c_14():20
             -->_2 mark#(0()) -> c_14():20
             -->_1 a__plus#(X1,X2) -> c_13():19
             -->_3 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_2 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_3 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_2 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_3 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_2 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_3 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_2 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_3 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_2 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
             -->_1 a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                           ,a__and#(a__isNat(M),isNat(N))
                                           ,a__isNat#(M)):7
             -->_1 a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N)):6
          
          13:S:mark#(s(X)) -> c_20(mark#(X))
             -->_1 mark#(tt()) -> c_21():21
             -->_1 mark#(0()) -> c_14():20
             -->_1 mark#(s(X)) -> c_20(mark#(X)):13
             -->_1 mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2)):12
             -->_1 mark#(isNat(X)) -> c_18(a__isNat#(X)):11
             -->_1 mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1)):10
             -->_1 mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1)):9
             -->_1 mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1)):8
          
          14:W:a__U11#(X1,X2) -> c_1()
             
          
          15:W:a__U21#(X1,X2,X3) -> c_3()
             
          
          16:W:a__and#(X1,X2) -> c_5()
             
          
          17:W:a__isNat#(X) -> c_7()
             
          
          18:W:a__isNat#(0()) -> c_8()
             
          
          19:W:a__plus#(X1,X2) -> c_13()
             
          
          20:W:mark#(0()) -> c_14()
             
          
          21:W:mark#(tt()) -> c_21()
             
          
        The following weak DPs constitute a sub-graph of the DG that is closed under successors. The DPs are removed.
          14: a__U11#(X1,X2) -> c_1()
          15: a__U21#(X1,X2,X3) -> c_3()
          16: a__and#(X1,X2) -> c_5()
          17: a__isNat#(X) -> c_7()
          18: a__isNat#(0()) -> c_8()
          19: a__plus#(X1,X2) -> c_13()
          20: mark#(0()) -> c_14()
          21: mark#(tt()) -> c_21()
* Step 4: Failure MAYBE
  + Considered Problem:
      - Strict DPs:
          a__U11#(tt(),N) -> c_2(mark#(N))
          a__U21#(tt(),M,N) -> c_4(a__plus#(mark(N),mark(M)),mark#(N),mark#(M))
          a__and#(tt(),X) -> c_6(mark#(X))
          a__isNat#(plus(V1,V2)) -> c_9(a__and#(a__isNat(V1),isNat(V2)),a__isNat#(V1))
          a__isNat#(s(V1)) -> c_10(a__isNat#(V1))
          a__plus#(N,0()) -> c_11(a__U11#(a__isNat(N),N),a__isNat#(N))
          a__plus#(N,s(M)) -> c_12(a__U21#(a__and(a__isNat(M),isNat(N)),M,N)
                                  ,a__and#(a__isNat(M),isNat(N))
                                  ,a__isNat#(M))
          mark#(U11(X1,X2)) -> c_15(a__U11#(mark(X1),X2),mark#(X1))
          mark#(U21(X1,X2,X3)) -> c_16(a__U21#(mark(X1),X2,X3),mark#(X1))
          mark#(and(X1,X2)) -> c_17(a__and#(mark(X1),X2),mark#(X1))
          mark#(isNat(X)) -> c_18(a__isNat#(X))
          mark#(plus(X1,X2)) -> c_19(a__plus#(mark(X1),mark(X2)),mark#(X1),mark#(X2))
          mark#(s(X)) -> c_20(mark#(X))
      - Weak TRS:
          a__U11(X1,X2) -> U11(X1,X2)
          a__U11(tt(),N) -> mark(N)
          a__U21(X1,X2,X3) -> U21(X1,X2,X3)
          a__U21(tt(),M,N) -> s(a__plus(mark(N),mark(M)))
          a__and(X1,X2) -> and(X1,X2)
          a__and(tt(),X) -> mark(X)
          a__isNat(X) -> isNat(X)
          a__isNat(0()) -> tt()
          a__isNat(plus(V1,V2)) -> a__and(a__isNat(V1),isNat(V2))
          a__isNat(s(V1)) -> a__isNat(V1)
          a__plus(N,0()) -> a__U11(a__isNat(N),N)
          a__plus(N,s(M)) -> a__U21(a__and(a__isNat(M),isNat(N)),M,N)
          a__plus(X1,X2) -> plus(X1,X2)
          mark(0()) -> 0()
          mark(U11(X1,X2)) -> a__U11(mark(X1),X2)
          mark(U21(X1,X2,X3)) -> a__U21(mark(X1),X2,X3)
          mark(and(X1,X2)) -> a__and(mark(X1),X2)
          mark(isNat(X)) -> a__isNat(X)
          mark(plus(X1,X2)) -> a__plus(mark(X1),mark(X2))
          mark(s(X)) -> s(mark(X))
          mark(tt()) -> tt()
      - Signature:
          {a__U11/2,a__U21/3,a__and/2,a__isNat/1,a__plus/2,mark/1,a__U11#/2,a__U21#/3,a__and#/2,a__isNat#/1,a__plus#/2
          ,mark#/1} / {0/0,U11/2,U21/3,and/2,isNat/1,plus/2,s/1,tt/0,c_1/0,c_2/1,c_3/0,c_4/3,c_5/0,c_6/1,c_7/0,c_8/0
          ,c_9/2,c_10/1,c_11/2,c_12/3,c_13/0,c_14/0,c_15/2,c_16/2,c_17/2,c_18/1,c_19/3,c_20/1,c_21/0}
      - Obligation:
          innermost runtime complexity wrt. defined symbols {a__U11#,a__U21#,a__and#,a__isNat#,a__plus#
          ,mark#} and constructors {0,U11,U21,and,isNat,plus,s,tt}
  + Applied Processor:
      EmptyProcessor
  + Details:
      The problem is still open.
MAYBE