#include <bits/stdc++.h>
using namespace std;
int main() {
  long long s, x;
  cin >> s >> x;
  bool f = (s == x);
  long long cnt = 1;
  while (s > 0) {
    int cs = s % 2;
    int cx = x % 2;
    if (cx == cs) {
      s /= 2;
      x /= 2;
      if (cx == 1)
        cnt *= 2;
      else if (x % 2 != s % 2)
        s--;
    } else {
      cnt = 0;
      s = 0;
    }
  }
  if (f) cnt -= 2;
  if (x != 0) cnt = 0;
  cout << cnt << "\n";
  return 0;
}

### Prompt

Your challenge is to write 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;
int main() {
  long long s, x;
  cin >> s >> x;
  bool f = (s == x);
  long long cnt = 1;
  while (s > 0) {
    int cs = s % 2;
    int cx = x % 2;
    if (cx == cs) {
      s /= 2;
      x /= 2;
      if (cx == 1)
        cnt *= 2;
      else if (x % 2 != s % 2)
        s--;
    } else {
      cnt = 0;
      s = 0;
    }
  }
  if (f) cnt -= 2;
  if (x != 0) cnt = 0;
  cout << cnt << "\n";
  return 0;
}

```