#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
  ll a, b;
  cin >> a >> b;
  if (a == 0) {
	  cout << 1 << endl;
	  return 0;
	}
  ll ans = 1;
  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) {
		  ans *= 2;
		}
	}
  cout << ans / 2 << endl;
  return 0;
}