(VAR x y z )
(RULES 
        gt(s(x), 0) -> true
        gt(0, y) -> false
        gt(s(x), s(y)) -> gt(x, y)
        divides(x, y) -> div(x, y, y)
        div(0, 0, z) -> true
        div(0, s(x), z) -> false
        div(s(x), 0, s(z)) -> div(s(x), s(z), s(z))
        div(s(x), s(y), z) -> div(x, y, z)
        prime(x) -> test(x, s(s(0)))
        test(x, y) -> if1(gt(x, y), x, y)
        if1(true, x, y) -> if2(divides(x, y), x, y)
        if1(false, x, y) -> true
        if2(true, x, y) -> false
        if2(false, x, y) -> test(x, s(y))
        
)