#include <bits/stdc++.h>
using namespace std;
int bitcnt(long long a) {
  int ans = 0;
  while (a > 0) {
    ans++;
    a = (a & (a - 1));
  }
  return ans;
}
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  long long s, x;
  cin >> s >> x;
  if (x > s) {
    cout << "0";
    return 0;
  }
  long long xcnt = bitcnt(x);
  if (s - x == 0) {
    cout << ((long long)1 << (xcnt)) - 2;
    return 0;
  }
  s -= x;
  if (((s / 2) & x) || (s % 2) == 1) {
    cout << "0";
    return 0;
  }
  cout << ((long long)1 << xcnt);
}

### 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 bitcnt(long long a) {
  int ans = 0;
  while (a > 0) {
    ans++;
    a = (a & (a - 1));
  }
  return ans;
}
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  long long s, x;
  cin >> s >> x;
  if (x > s) {
    cout << "0";
    return 0;
  }
  long long xcnt = bitcnt(x);
  if (s - x == 0) {
    cout << ((long long)1 << (xcnt)) - 2;
    return 0;
  }
  s -= x;
  if (((s / 2) & x) || (s % 2) == 1) {
    cout << "0";
    return 0;
  }
  cout << ((long long)1 << xcnt);
}

```