TRS:
 { f(a(), g(y)) -> g(g(y)),
   f(g(x), a()) -> f(x, g(a())),
  f(g(x), g(y)) -> h(g(y), x, g(y)),
  h(g(x), y, z) -> f(y, h(x, y, z)),
   h(a(), y, z) -> z}
 Fail