#include <bits/stdc++.h>
using namespace std;
int main(void) {
  long long s, x;
  while (scanf("%I64d %I64d", &s, &x) != EOF) {
    long long res = 1;
    int curs, curx, was = 0, k;
    for (k = 60; k >= 0; k--) {
      curx = (x >> k) & 1;
      curs = (s >> k) & 1;
      res <<= curx;
      if (was == 0) {
        if (curs == 0 && curx == 1) res = 0;
        if (curs == 1 && curx == 0) was = 1;
      } else {
        if (curs == 1 && curx == 1) res = 0;
        if (curs == 0 && curx == 0) was = 0;
      }
    }
    if (s == x) res -= 2;
    if (was) res = 0;
    printf("%I64d\n", res);
  }
  return 0;
}
