TRS:
 {cond(true(), x, y) -> cond(gr(x, y), p(x), y),
          gr(0(), x) -> false(),
       gr(s(x), 0()) -> true(),
      gr(s(x), s(y)) -> gr(x, y),
              p(0()) -> 0(),
             p(s(x)) -> x}
 Fail