(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))
        
)