(VAR x y )
(RULES 
        f(0) -> 0
        f(s(0)) -> s(0)
        f(s(s(x))) -> p(h(g(x)))
        g(0) -> pair(s(0), s(0))
        g(s(x)) -> h(g(x))
        h(x) -> pair(+(p(x), q(x)), p(x))
        p(pair(x, y)) -> x
        q(pair(x, y)) -> y
        +(x, 0) -> x
        +(x, s(y)) -> s(+(x, y))
        f(s(s(x))) -> +(p(g(x)), q(g(x)))
        g(s(x)) -> pair(+(p(g(x)), q(g(x))), p(g(x)))
        
)