#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
  ll a, b;
  cin >> a >> b;
  ll ans   = 1;
  bool flg = false;
  for (ll i = 1; i < (1LL << 31); i = i << 1) {
	  ll A = i & a;
	  ll B = i & b;
	  if (A > B) {
		  ans = 0;
		  break;
		}
	  if (A < B) {
		  if (!flg) {
			  flg = true;
			} else {
			  ans *= 2;
			}
		}
	}
  if (a != 0) {
	  ans /= 2;
	}
  cout << ans << endl;
  return 0;
}