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