TRS:
 {       +(x, 0()) -> x,
         +(0(), x) -> x,
     +(s(x), s(y)) -> s(s(+(x, y))),
         *(x, 0()) -> 0(),
         *(0(), x) -> 0(),
     *(s(x), s(y)) -> s(+(*(x, y), +(x, y))),
        sum(nil()) -> 0(),
   sum(cons(x, l)) -> +(x, sum(l)),
       prod(nil()) -> s(0()),
  prod(cons(x, l)) -> *(x, prod(l))}
 Fail