YES
O(n^3)
TRS:
 {f(a(), f(f(a(), x), a())) -> f(f(a(), f(a(), x)), a())}
 DUP: We consider a non-duplicating system.
  Trs:
   {f(a(), f(f(a(), x), a())) -> f(f(a(), f(a(), x)), a())}
  Matrix Interpretation:
   Interpretation class: triangular
         [0]
   [a] = [0]
         [0]
   
       [X5]  [X2]    [1 0 0][X5]   [1 0 1][X2]   [0]
   [f]([X4], [X1]) = [0 0 0][X4] + [0 0 0][X1] + [0]
       [X3]  [X0]    [0 0 1][X3]   [0 0 1][X0]   [1]
   
   
   Qed