YES
O(n^2)
TRS:
 {   f(X, X) -> c(X),
  f(X, c(X)) -> f(s(X), X),
  f(s(X), X) -> f(X, a(X))}
 DUP: We consider a non-duplicating system.
  Trs:
   {   f(X, X) -> c(X),
    f(X, c(X)) -> f(s(X), X),
    f(s(X), X) -> f(X, a(X))}
  Matrix Interpretation:
   Interpretation class: triangular
       [X1]    [1 2][X1]   [2]
   [c]([X0]) = [0 0][X0] + [0]
   
       [X1]    [1 2][X1]   [1]
   [s]([X0]) = [0 0][X0] + [0]
   
       [X1]    [1 0][X1]   [0]
   [a]([X0]) = [0 0][X0] + [0]
   
       [X3]  [X1]    [1 2][X3]   [1 0][X1]   [3]
   [f]([X2], [X0]) = [0 0][X2] + [0 0][X0] + [0]
   
   
   Qed