#include <bits/stdc++.h>
using namespace std;
long long s, x;
void err() {
  cout << 0;
  exit(0);
}
int main() {
  cin >> s >> x;
  long long y = s - x;
  if (y % 2) err();
  y /= 2;
  long long ans = 1;
  for (long long i = 0; i <= 40; i++) {
    if (((y >> i) & 1) && ((x >> i) & 1)) err();
    if (((y >> i) & 1) == 0 && ((x >> i) & 1)) {
      ans = 1ll * ans * 2;
    }
  }
  int flag = 0;
  for (long long i = 0; i <= 40; i++) {
    if ((y >> i) & 1) flag = 1;
  }
  if (!flag) ans -= 2;
  cout << ans;
}

### Prompt

Your task is to create 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;
long long s, x;
void err() {
  cout << 0;
  exit(0);
}
int main() {
  cin >> s >> x;
  long long y = s - x;
  if (y % 2) err();
  y /= 2;
  long long ans = 1;
  for (long long i = 0; i <= 40; i++) {
    if (((y >> i) & 1) && ((x >> i) & 1)) err();
    if (((y >> i) & 1) == 0 && ((x >> i) & 1)) {
      ans = 1ll * ans * 2;
    }
  }
  int flag = 0;
  for (long long i = 0; i <= 40; i++) {
    if ((y >> i) & 1) flag = 1;
  }
  if (!flag) ans -= 2;
  cout << ans;
}

```