#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  long long sum, xr;
  cin >> sum >> xr;
  long long dp[2] = {1, 0};
  for (int bit = 0; bit < 50; bit++) {
    long long ndp[2] = {0, 0};
    int needSum = (sum >> bit) & 1;
    int needXor = (xr >> bit) & 1;
    for (int was = 0; was < 2; was++) {
      for (int b1 = 0; b1 < 2; b1++) {
        for (int b2 = 0; b2 < 2; b2++) {
          int mySum = (b1 + b2 + was) % 2;
          int myXor = b1 ^ b2;
          if (myXor == needXor && mySum == needSum) {
            ndp[(b1 + b2 + was) >> 1] += dp[was];
          }
        }
      }
    }
    for (int _n(2), i(0); i < _n; i++) dp[i] = ndp[i];
  }
  cout << (dp[0] - (sum == xr ? 2 : 0)) << endl;
  return 0;
}
