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