(VAR x y z )
(RULES 
        f(x, y, z) -> g(<=(x, y), x, y, z)
        g(true, x, y, z) -> z
        g(false, x, y, z) -> f(f(p(x), y, z), f(p(y), z, x), f(p(z), x, y))
        p(0) -> 0
        p(s(x)) -> x
        
)