#include <bits/stdc++.h>
using namespace std;
long long s, x, da, xo, ans;
int main() {
  cin >> s >> x;
  if (s < x || (s - x) % 2) {
    cout << 0;
    return 0;
  }
  da = (s - x) / 2;
  xo = x;
  ans = 1;
  while (xo || da) {
    if (da % 2 == 1 && xo % 2 == 1) {
      cout << 0;
      return 0;
    }
    if (da % 2 == 0 && xo % 2 == 1) ans *= 2;
    da /= 2;
    xo /= 2;
  }
  if (s == x) ans -= 2;
  cout << ans << endl;
}

### Prompt

In Cpp, your task is to solve 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;
long long s, x, da, xo, ans;
int main() {
  cin >> s >> x;
  if (s < x || (s - x) % 2) {
    cout << 0;
    return 0;
  }
  da = (s - x) / 2;
  xo = x;
  ans = 1;
  while (xo || da) {
    if (da % 2 == 1 && xo % 2 == 1) {
      cout << 0;
      return 0;
    }
    if (da % 2 == 0 && xo % 2 == 1) ans *= 2;
    da /= 2;
    xo /= 2;
  }
  if (s == x) ans -= 2;
  cout << ans << endl;
}

```