#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2 * 1e5 + 10;
const int INF = 0x3f3f3f3f;
int main() {
  long long s, x;
  cin >> s >> x;
  long long ans = 0;
  if (x == s) ans -= 2;
  s -= x;
  if (s % 2) {
    puts("0");
    return 0;
  }
  s /= 2;
  long long t = 1;
  for (int i = 0; i < 63; i++) {
    long long tmp = 1LL << i;
    if ((tmp & x) && !(s & tmp)) {
      t <<= 1;
    } else if (tmp & x) {
      puts("0");
      return 0;
    }
  }
  ans += t;
  cout << ans << endl;
  return 0;
}

### 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;
const int MAXN = 2 * 1e5 + 10;
const int INF = 0x3f3f3f3f;
int main() {
  long long s, x;
  cin >> s >> x;
  long long ans = 0;
  if (x == s) ans -= 2;
  s -= x;
  if (s % 2) {
    puts("0");
    return 0;
  }
  s /= 2;
  long long t = 1;
  for (int i = 0; i < 63; i++) {
    long long tmp = 1LL << i;
    if ((tmp & x) && !(s & tmp)) {
      t <<= 1;
    } else if (tmp & x) {
      puts("0");
      return 0;
    }
  }
  ans += t;
  cout << ans << endl;
  return 0;
}

```