YES
O(n^3)
TRS:
 {
  U12(tt(), M, N) -> s(plus(activate(N), activate(M))),
      activate(X) -> X,
  U11(tt(), M, N) -> U12(tt(), activate(M), activate(N)),
    plus(N, s(M)) -> U11(tt(), M, N),
     plus(N, 0()) -> N
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
    U12(tt(), M, N) -> s(plus(activate(N), activate(M))),
        activate(X) -> X,
    U11(tt(), M, N) -> U12(tt(), activate(M), activate(N)),
      plus(N, s(M)) -> U11(tt(), M, N),
       plus(N, 0()) -> N
   }
  Matrix Interpretation:
   Interpretation class: triangular
         [1]
   [0] = [0]
         [1]
   
          [X5]  [X2]    [1 0 0][X5]   [1 0 3][X2]   [0]
   [plus]([X4], [X1]) = [0 1 0][X4] + [0 0 0][X1] + [0]
          [X3]  [X0]    [0 0 1][X3]   [0 0 1][X0]   [0]
   
       [X2]    [1 0 0][X2]   [0]
   [s]([X1]) = [0 0 0][X1] + [0]
       [X0]    [0 0 1][X0]   [3]
   
         [X8]  [X5]  [X2]    [1 3 0][X8]   [1 0 3][X5]   [1 0 0][X2]   [0]
   [U11]([X7], [X4], [X1]) = [0 0 0][X7] + [0 0 0][X4] + [0 0 0][X1] + [0]
         [X6]  [X3]  [X0]    [0 0 0][X6]   [0 0 1][X3]   [0 0 1][X0]   [3]
   
              [X2]    [1 0 0][X2]   [1]
   [activate]([X1]) = [0 1 0][X1] + [0]
              [X0]    [0 0 1][X0]   [0]
   
          [1]
   [tt] = [2]
          [0]
   
         [X8]  [X5]  [X2]    [1 0 0][X8]   [1 0 3][X5]   [1 0 0][X2]   [2]
   [U12]([X7], [X4], [X1]) = [0 0 0][X7] + [0 0 0][X4] + [0 0 0][X1] + [0]
         [X6]  [X3]  [X0]    [0 0 0][X6]   [0 0 1][X3]   [0 0 1][X0]   [3]
   
   
   Qed