#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long s, x;
  cin >> s >> x;
  unsigned long long ans = 1;
  int dos = (s == x) << 1;
  bool carry = 0;
  for (int i = 0; i < 41; i++) {
    int sb = s & 1;
    int xb = x & 1;
    if (!carry) {
      if (sb == 1 && xb == 1) ans *= 2;
      if (sb != xb) ans = 0;
      if (sb == 0 && xb == 0) carry = ((s & 2) != (x & 2));
    } else {
      if (sb == 0 && xb == 1) ans *= 2;
      if (sb == xb) ans = 0;
      if (sb == 1 && xb == 0) carry = ((s & 2) != (x & 2));
    }
    s >>= 1;
    x >>= 1;
  }
  cout << ans - dos << ' ';
}

### 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;
int main() {
  unsigned long long s, x;
  cin >> s >> x;
  unsigned long long ans = 1;
  int dos = (s == x) << 1;
  bool carry = 0;
  for (int i = 0; i < 41; i++) {
    int sb = s & 1;
    int xb = x & 1;
    if (!carry) {
      if (sb == 1 && xb == 1) ans *= 2;
      if (sb != xb) ans = 0;
      if (sb == 0 && xb == 0) carry = ((s & 2) != (x & 2));
    } else {
      if (sb == 0 && xb == 1) ans *= 2;
      if (sb == xb) ans = 0;
      if (sb == 1 && xb == 0) carry = ((s & 2) != (x & 2));
    }
    s >>= 1;
    x >>= 1;
  }
  cout << ans - dos << ' ';
}

```