YES
O(n^5)
TRS:
 {
     a__f(X1, X2, X3) -> f(X1, X2, X3),
      a__f(a(), X, X) -> a__f(X, a__b(), b()),
               a__b() -> b(),
               a__b() -> a(),
            mark(b()) -> a__b(),
            mark(a()) -> a(),
  mark(f(X1, X2, X3)) -> a__f(X1, mark(X2), X3)
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
       a__f(X1, X2, X3) -> f(X1, X2, X3),
        a__f(a(), X, X) -> a__f(X, a__b(), b()),
                 a__b() -> b(),
                 a__b() -> a(),
              mark(b()) -> a__b(),
              mark(a()) -> a(),
    mark(f(X1, X2, X3)) -> a__f(X1, mark(X2), X3)
   }
  Matrix Interpretation:
   Interpretation class: triangular
       [X14]  [X9]  [X4]    [1 1 1 1 0][X14]   [1 0 1 0 0][X9]   [1 1 0 1 0][X4]   [0]
       [X13]  [X8]  [X3]    [0 0 0 0 0][X13]   [0 0 0 0 0][X8]   [0 0 0 0 0][X3]   [1]
   [f]([X12], [X7], [X2]) = [0 0 0 0 0][X12] + [0 0 0 0 1][X7] + [0 0 0 0 0][X2] + [1]
       [X11]  [X6]  [X1]    [0 0 0 0 0][X11]   [0 0 0 0 0][X6]   [0 0 0 0 0][X1]   [1]
       [X10]  [X5]  [X0]    [0 0 0 0 1][X10]   [0 0 0 0 1][X5]   [0 0 0 0 0][X0]   [1]
   
          [X4]    [1 0 1 0 1][X4]   [0]
          [X3]    [0 1 1 0 0][X3]   [0]
   [mark]([X2]) = [0 0 0 0 1][X2] + [0]
          [X1]    [0 0 0 0 0][X1]   [1]
          [X0]    [0 0 0 0 1][X0]   [0]
   
         [0]
         [1]
   [a] = [1]
         [1]
         [1]
   
         [0]
         [0]
   [b] = [1]
         [0]
         [1]
   
            [1]
            [1]
   [a__b] = [1]
            [1]
            [1]
   
          [X14]  [X9]  [X4]    [1 1 1 1 0][X14]   [1 0 1 0 0][X9]   [1 1 0 1 0][X4]   [1]
          [X13]  [X8]  [X3]    [0 0 0 0 0][X13]   [0 0 0 0 0][X8]   [0 0 0 0 0][X3]   [1]
   [a__f]([X12], [X7], [X2]) = [0 0 0 0 1][X12] + [0 0 0 0 1][X7] + [0 0 0 0 0][X2] + [1]
          [X11]  [X6]  [X1]    [0 0 0 0 0][X11]   [0 0 0 0 0][X6]   [0 0 0 0 0][X1]   [1]
          [X10]  [X5]  [X0]    [0 0 0 0 1][X10]   [0 0 0 0 1][X5]   [0 0 0 0 0][X0]   [1]
   
   
   Qed