(VAR x y )
(RULES 
        plus(x, 0) -> x
        plus(x, s(y)) -> s(plus(x, y))
        d(0) -> 0
        d(s(x)) -> s(s(d(x)))
        q(0) -> 0
        q(s(x)) -> s(plus(q(x), d(x)))
        
)