#include <bits/stdc++.h>
long long a, b;
long long B[100], Z[100];
int main() {
  scanf("%I64d%I64d", &a, &b);
  B[0] = 1;
  for (int i = 0; i < 60; i++) {
    if ((a & (1ll << i)) == 0 && (b & (1ll << i)) == 0) {
      B[i + 1] = B[i];
      Z[i + 1] = B[i];
    }
    if ((a & (1ll << i)) == 0 && (b & (1ll << i)) != 0) {
      B[i + 1] = 0;
      Z[i + 1] = Z[i] * 2;
    }
    if ((a & (1ll << i)) != 0 && (b & (1ll << i)) == 0) {
      B[i + 1] = Z[i];
      Z[i + 1] = Z[i];
    }
    if ((a & (1ll << i)) != 0 && (b & (1ll << i)) != 0) {
      B[i + 1] = B[i] * 2;
      Z[i + 1] = 0;
    }
  }
  if (a == b) B[60] -= 2;
  printf("%I64d", B[60]);
}
