(VAR x y )
(RULES 
        prime(0) -> false
        prime(s(0)) -> false
        prime(s(s(x))) -> prime1(s(s(x)), s(x))
        prime1(x, 0) -> false
        prime1(x, s(0)) -> true
        prime1(x, s(s(y))) -> and(not(divp(s(s(y)), x)), prime1(x, s(y)))
        divp(x, y) -> =(rem(x, y), 0)
        
)