(VAR x y z ) (RULES plus(x, 0) -> x plus(0, y) -> y plus(s(x), y) -> s(plus(x, y)) times(0, y) -> 0 times(s(0), y) -> y times(s(x), y) -> plus(y, times(x, y)) div(0, y) -> 0 div(x, y) -> quot(x, y, y) quot(0, s(y), z) -> 0 quot(s(x), s(y), z) -> quot(x, y, z) quot(x, 0, s(z)) -> s(div(x, s(z))) div(div(x, y), z) -> div(x, times(y, z)) eq(0, 0) -> true eq(s(x), 0) -> false eq(0, s(y)) -> false eq(s(x), s(y)) -> eq(x, y) divides(y, x) -> eq(x, times(div(x, y), y)) prime(s(s(x))) -> pr(s(s(x)), s(x)) pr(x, s(0)) -> true pr(x, s(s(y))) -> if(divides(s(s(y)), x), x, s(y)) if(true, x, y) -> false if(false, x, y) -> pr(x, y) )