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