#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int s, x;
  cin >> s >> x;
  long long int e = 0;
  bool ok = true;
  int c[2][2] = {};
  for (int i = 0; i < 50; i++) {
    bool si = s & (1LL << i), xi = x & (1LL << i);
    if (si == 0 && xi == 0) ok &= e <= 1, e = 1;
    if (si == 0 && xi == 1) ok &= e > 0, e = 2;
    if (si == 1 && xi == 0) ok &= e > 0, e = 1;
    if (si == 1 && xi == 1) ok &= e <= 1, e = 0;
    c[si][xi]++;
  }
  long long int ans = 0;
  if (ok) {
    ans = (1LL << (c[0][1] + c[1][1]));
    ans -= (s == x) * 2;
  }
  cout << max(ans, 0LL) << "\n";
  return 0;
}
