#include <bits/stdc++.h>
using namespace std;
const int N = 300500;
long long x, s;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> s >> x;
  int cnt = 0;
  long long cur = x;
  for (int i = 50; i >= 0; --i) {
    if ((x & (1ll << i)) != 0) {
      cnt++;
    } else {
      if (cur + (1ll << (i + 1)) <= s) {
        cur += (1ll << (i + 1));
      }
    }
  }
  long long answer = (1ll << cnt);
  if (cur == s) {
    if (s == x) {
      answer -= 2;
    }
    cout << answer;
  } else {
    cout << 0;
  }
  return 0;
}

### Prompt

Generate a cpp solution to the following problem:

Two positive integers a and b have a sum of s and a bitwise XOR of x. How many possible values are there for the ordered pair (a, b)?

Input

The first line of the input contains two integers s and x (2 ≤ s ≤ 1012, 0 ≤ x ≤ 1012), the sum and bitwise xor of the pair of positive integers, respectively.

Output

Print a single integer, the number of solutions to the given conditions. If no solutions exist, print 0.

Examples

Input

9 5


Output

4


Input

3 3


Output

2


Input

5 2


Output

0

Note

In the first sample, we have the following solutions: (2, 7), (3, 6), (6, 3), (7, 2).

In the second sample, the only solutions are (1, 2) and (2, 1).

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
const int N = 300500;
long long x, s;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> s >> x;
  int cnt = 0;
  long long cur = x;
  for (int i = 50; i >= 0; --i) {
    if ((x & (1ll << i)) != 0) {
      cnt++;
    } else {
      if (cur + (1ll << (i + 1)) <= s) {
        cur += (1ll << (i + 1));
      }
    }
  }
  long long answer = (1ll << cnt);
  if (cur == s) {
    if (s == x) {
      answer -= 2;
    }
    cout << answer;
  } else {
    cout << 0;
  }
  return 0;
}

```