And now you're left with just 2^31 - 1, -2^31, -2^31 + 1, 0. If you define f(f(0)) = 0, then you have only 3 numbers and you need 4 for a chain. The parent of

And now you're left with just 2^31 - 1, -2^31, -2^31 + 1, 0. If you define f(f(0)) = 0, then you have only 3 numbers and you need 4 for a chain. The parent of your post explicitly said: all but one number (2^n - 1) correct.