(VAR x y )
(RULES 
        cond(true, x, y) -> cond(gr(x, y), p(x), s(y))
        gr(0, x) -> false
        gr(s(x), 0) -> true
        gr(s(x), s(y)) -> gr(x, y)
        p(0) -> 0
        p(s(x)) -> x
        
)