(VAR x y z )
(RULES 
        b(a, f(b(b(z, y), a))) -> z
        c(c(z, x, a), a, y) -> f(f(c(y, a, f(c(z, y, x)))))
        f(f(c(a, y, z))) -> b(y, b(z, z))
        
)