#include <bits/stdc++.h>
using namespace std;
long long dp[55][2];
int main() {
  long long X, Y;
  scanf("%lld %lld", &Y, &X);
  dp[51][0] = 1;
  for (int i = 50; i >= 0; i--) {
    for (int flag = 0; flag <= 1; flag++) {
      bool x = (X >> i) & 1, y = (Y >> i) & 1;
      if (x)
        dp[i][flag] += dp[i + 1][(flag + 1) / 2] * (flag != y) * 2;
      else {
        dp[i][flag] += dp[i + 1][(flag + 2) / 2] * (flag == y);
        dp[i][flag] += dp[i + 1][0] * (flag == y);
      }
    }
  }
  if (!X) assert(dp[0][0] - (X == Y) * 2 == (!(Y & 1)));
  printf("%lld\n", dp[0][0] - (X == Y) * 2);
  return 0;
}
