TRS:
 { times(x, 0()) -> 0(),
  times(x, s(y)) -> plus(times(x, y), x),
    plus(x, 0()) -> x,
    plus(0(), x) -> x,
   plus(x, s(y)) -> s(plus(x, y)),
   plus(s(x), y) -> s(plus(x, y))}
 Fail