YES
O(n^4)
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] = [0]
         [0]
   
          [X7]  [X3]    [1 0 0 0][X7]   [1 3 0 0][X3]   [0]
          [X6]  [X2]    [0 1 0 0][X6]   [0 1 0 0][X2]   [0]
   [plus]([X5], [X1]) = [0 0 1 0][X5] + [0 0 0 0][X1] + [0]
          [X4]  [X0]    [0 0 0 1][X4]   [0 0 0 0][X0]   [0]
   
       [X3]    [1 0 0 0][X3]   [0]
       [X2]    [0 1 0 0][X2]   [3]
   [s]([X1]) = [0 0 0 0][X1] + [0]
       [X0]    [0 0 0 0][X0]   [0]
   
         [X11]  [X7]  [X3]    [1 2 0 2][X11]   [1 3 0 0][X7]   [1 0 0 0][X3]   [0]
         [X10]  [X6]  [X2]    [0 1 0 0][X10]   [0 1 0 0][X6]   [0 1 0 0][X2]   [1]
   [U11]([ X9], [X5], [X1]) = [0 0 0 0][X9] + [0 0 0 0][X5] + [0 0 1 0][X1] + [0]
         [ X8]  [X4]  [X0]    [0 0 0 0][X8]   [0 0 0 0][X4]   [0 0 0 0][X0]   [0]
   
              [X3]    [1 0 0 0][X3]   [1]
              [X2]    [0 1 0 0][X2]   [0]
   [activate]([X1]) = [0 0 1 0][X1] + [0]
              [X0]    [0 0 0 1][X0]   [0]
   
          [0]
          [2]
   [tt] = [0]
          [2]
   
         [X11]  [X7]  [X3]    [1 0 0 2][X11]   [1 3 0 0][X7]   [1 0 0 0][X3]   [0]
         [X10]  [X6]  [X2]    [0 0 0 0][X10]   [0 1 0 0][X6]   [0 1 0 0][X2]   [3]
   [U12]([ X9], [X5], [X1]) = [0 0 0 0][X9] + [0 0 0 0][X5] + [0 0 0 0][X1] + [0]
         [ X8]  [X4]  [X0]    [0 0 0 0][X8]   [0 0 0 0][X4]   [0 0 0 0][X0]   [0]
   
   
   Qed