TRS:
 {    +(0(), y) -> y,
     +(s(x), y) -> s(+(x, y)),
      *(x, 0()) -> 0(),
     *(x, s(y)) -> +(x, *(x, y)),
     twice(0()) -> 0(),
    twice(s(x)) -> s(s(twice(x))),
      -(x, 0()) -> x,
  -(s(x), s(y)) -> -(x, y),
        f(s(x)) -> f(-(*(s(s(x)), s(s(x))), +(*(s(x), s(s(x))), s(s(0())))))}
 Fail