#include <bits/stdc++.h>
using namespace std;
long long s, x;
bool u[60];
long long ret = 1;
int main() {
  cin >> s >> x;
  bool f = (s == x);
  for (int i = 0; i < (60); i++) {
    if ((x >> i) & 1) {
      u[i] = 1;
      s -= (1LL << i);
      ret *= 2;
    }
  }
  for (int i = 0; i < (60); i++) {
    if (!u[i]) {
      if (s & (1LL << (i + 1))) {
        s -= 1LL << (i + 1);
      }
    }
  }
  if (s != 0)
    ret = 0;
  else if (f)
    ret -= 2;
  cout << ret << endl;
  return 0;
}

### Prompt

Please formulate 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;
bool u[60];
long long ret = 1;
int main() {
  cin >> s >> x;
  bool f = (s == x);
  for (int i = 0; i < (60); i++) {
    if ((x >> i) & 1) {
      u[i] = 1;
      s -= (1LL << i);
      ret *= 2;
    }
  }
  for (int i = 0; i < (60); i++) {
    if (!u[i]) {
      if (s & (1LL << (i + 1))) {
        s -= 1LL << (i + 1);
      }
    }
  }
  if (s != 0)
    ret = 0;
  else if (f)
    ret -= 2;
  cout << ret << endl;
  return 0;
}

```