(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)
        
)