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))
  Matrix Interpretation Processor: dim=1
   
   interpretation:
    [lessleaves#](x0, x1) = 2x0 + 2x1 + 5/2,
    
    [concat#](x0, x1) = 3x0 + 2x1,
    
    [true] = 0,
    
    [false] = 0,
    
    [lessleaves](x0, x1) = 0,
    
    [cons](x0, x1) = 3/2x0 + x1 + 3/2,
    
    [concat](x0, x1) = x0 + x1,
    
    [leaf] = 0
   orientation:
    concat#(cons(U,V),Y) = 9/2U + 3V + 2Y + 9/2 >= 3V + 2Y = concat#(V,Y)
    
    lessleaves#(cons(U,V),cons(W,Z)) = 3U + 2V + 3W + 2Z + 17/2 >= 3W + 2Z = concat#(W,Z)
    
    lessleaves#(cons(U,V),cons(W,Z)) = 3U + 2V + 3W + 2Z + 17/2 >= 3U + 2V = concat#(U,V)
    
    lessleaves#(cons(U,V),cons(W,Z)) = 3U + 2V + 3W + 2Z + 17/2 >= 2U + 2V + 2W + 2Z + 5/2 = lessleaves#(concat(U,V),concat(W,Z))
    
    concat(leaf(),Y) = Y >= Y = Y
    
    concat(cons(U,V),Y) = 3/2U + V + Y + 3/2 >= 3/2U + V + Y + 3/2 = 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