#include <bits/stdc++.h>
using namespace std;
int main() {
  long long x, y, ans = 1;
  cin >> x >> y;
  x -= y;
  for (int i = 0; i < 50; i++) {
    if (y & (1LL << i)) ans *= 2LL;
  }
  if (!x) ans -= 2LL;
  for (int i = 0; i < 50; i++) {
    if (x & (1LL << i)) {
      if (!i)
        ans = 0;
      else if (y & (1LL << (i - 1)))
        ans = 0;
    }
  }
  cout << ans;
}

### 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;
int main() {
  long long x, y, ans = 1;
  cin >> x >> y;
  x -= y;
  for (int i = 0; i < 50; i++) {
    if (y & (1LL << i)) ans *= 2LL;
  }
  if (!x) ans -= 2LL;
  for (int i = 0; i < 50; i++) {
    if (x & (1LL << i)) {
      if (!i)
        ans = 0;
      else if (y & (1LL << (i - 1)))
        ans = 0;
    }
  }
  cout << ans;
}

```