TRS:
 {g(0(), f(x, x)) -> x,
       g(x, s(y)) -> g(f(x, y), 0()),
       g(s(x), y) -> g(f(x, y), 0()),
  g(f(x, y), 0()) -> f(g(x, 0()), g(y, 0()))}
 Fail