TRS:
 {           p(0()) -> 0(),
            p(s(x)) -> x,
         le(0(), y) -> true(),
      le(s(x), 0()) -> false(),
     le(s(x), s(y)) -> le(x, y),
      minus(x, 0()) -> x,
     minus(x, s(y)) -> if(le(x, s(y)), 0(), p(minus(x, p(s(y))))),
   if(true(), x, y) -> x,
  if(false(), x, y) -> y}
 Fail