YES

Problem:
 concat(leaf(),Y) -> Y
 concat(cons(U,V),Y) -> cons(U,concat(V,Y))
 lessleaves(X,leaf()) -> false()
 lessleaves(leaf(),cons(W,Z)) -> true()
 lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))

Proof:
 DP Processor:
  DPs:
   concat#(cons(U,V),Y) -> concat#(V,Y)
   lessleaves#(cons(U,V),cons(W,Z)) -> concat#(W,Z)
   lessleaves#(cons(U,V),cons(W,Z)) -> concat#(U,V)
   lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z))
  TRS:
   concat(leaf(),Y) -> Y
   concat(cons(U,V),Y) -> cons(U,concat(V,Y))
   lessleaves(X,leaf()) -> false()
   lessleaves(leaf(),cons(W,Z)) -> true()
   lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
  EDG Processor:
   DPs:
    concat#(cons(U,V),Y) -> concat#(V,Y)
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(W,Z)
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(U,V)
    lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z))
   TRS:
    concat(leaf(),Y) -> Y
    concat(cons(U,V),Y) -> cons(U,concat(V,Y))
    lessleaves(X,leaf()) -> false()
    lessleaves(leaf(),cons(W,Z)) -> true()
    lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
   graph:
    lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z)) ->
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(W,Z)
    lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z)) ->
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(U,V)
    lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z)) ->
    lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z))
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(W,Z) ->
    concat#(cons(U,V),Y) -> concat#(V,Y)
    lessleaves#(cons(U,V),cons(W,Z)) -> concat#(U,V) ->
    concat#(cons(U,V),Y) -> concat#(V,Y)
    concat#(cons(U,V),Y) -> concat#(V,Y) -> concat#(cons(U,V),Y) -> concat#(V,Y)
   SCC Processor:
    #sccs: 2
    #rules: 2
    #arcs: 6/16
    DPs:
     lessleaves#(cons(U,V),cons(W,Z)) -> lessleaves#(concat(U,V),concat(W,Z))
    TRS:
     concat(leaf(),Y) -> Y
     concat(cons(U,V),Y) -> cons(U,concat(V,Y))
     lessleaves(X,leaf()) -> false()
     lessleaves(leaf(),cons(W,Z)) -> true()
     lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
    Matrix Interpretation Processor:
     dimension: 1
     interpretation:
      [lessleaves#](x0, x1) = x1,
      
      [true] = 0,
      
      [false] = 0,
      
      [lessleaves](x0, x1) = 0,
      
      [cons](x0, x1) = x0 + x1 + 1,
      
      [concat](x0, x1) = x0 + x1,
      
      [leaf] = 0
     orientation:
      lessleaves#(cons(U,V),cons(W,Z)) = W + Z + 1 >= W + Z = lessleaves#(concat(U,V),concat(W,Z))
      
      concat(leaf(),Y) = Y >= Y = Y
      
      concat(cons(U,V),Y) = U + V + Y + 1 >= U + V + Y + 1 = cons(U,concat(V,Y))
      
      lessleaves(X,leaf()) = 0 >= 0 = false()
      
      lessleaves(leaf(),cons(W,Z)) = 0 >= 0 = true()
      
      lessleaves(cons(U,V),cons(W,Z)) = 0 >= 0 = lessleaves(concat(U,V),concat(W,Z))
     problem:
      DPs:
       
      TRS:
       concat(leaf(),Y) -> Y
       concat(cons(U,V),Y) -> cons(U,concat(V,Y))
       lessleaves(X,leaf()) -> false()
       lessleaves(leaf(),cons(W,Z)) -> true()
       lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
     Qed
    
    DPs:
     concat#(cons(U,V),Y) -> concat#(V,Y)
    TRS:
     concat(leaf(),Y) -> Y
     concat(cons(U,V),Y) -> cons(U,concat(V,Y))
     lessleaves(X,leaf()) -> false()
     lessleaves(leaf(),cons(W,Z)) -> true()
     lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
    Subterm Criterion Processor:
     simple projection:
      pi(concat#) = 0
     problem:
      DPs:
       
      TRS:
       concat(leaf(),Y) -> Y
       concat(cons(U,V),Y) -> cons(U,concat(V,Y))
       lessleaves(X,leaf()) -> false()
       lessleaves(leaf(),cons(W,Z)) -> true()
       lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
     Qed