#include <bits/stdc++.h>
using namespace std;
int main() {
  long long s, x;
  ios::sync_with_stdio(false);
  long long ans, y;
  while (cin >> s >> x) {
    ans = 1;
    y = 0;
    if (s == x) y = 2;
    if (s - x < 0 || (s - x) % 2)
      cout << "0" << endl;
    else if (((s - x) / 2) & x)
      cout << "0" << endl;
    else {
      while (x) {
        if (x % 2 == 1) ans *= 2;
        x /= 2;
        ;
      }
      ans -= y;
      cout << ans << endl;
    }
  }
}

### Prompt

Construct a CPP code solution to the problem outlined:

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;
int main() {
  long long s, x;
  ios::sync_with_stdio(false);
  long long ans, y;
  while (cin >> s >> x) {
    ans = 1;
    y = 0;
    if (s == x) y = 2;
    if (s - x < 0 || (s - x) % 2)
      cout << "0" << endl;
    else if (((s - x) / 2) & x)
      cout << "0" << endl;
    else {
      while (x) {
        if (x % 2 == 1) ans *= 2;
        x /= 2;
        ;
      }
      ans -= y;
      cout << ans << endl;
    }
  }
}

```