(VAR x y )
(RULES 
        fac(0) -> 1
        fac(s(x)) -> *(s(x), fac(x))
        floop(0, y) -> y
        floop(s(x), y) -> floop(x, *(s(x), y))
        *(x, 0) -> 0
        *(x, s(y)) -> +(*(x, y), x)
        +(x, 0) -> x
        +(x, s(y)) -> s(+(x, y))
        1 -> s(0)
        fac(0) -> s(0)
        
)