(VAR c x y )
(RULES 
        lt(0, s(x)) -> true
        lt(x, 0) -> false
        lt(s(x), s(y)) -> lt(x, y)
        fac(x) -> help(x, 0)
        help(x, c) -> if(lt(c, x), x, c)
        if(true, x, c) -> times(s(c), help(x, s(c)))
        if(false, x, c) -> s(0)
        
)