#include <bits/stdc++.h>
using namespace std;
long long s, x;
long long car[2];
int main() {
  cin >> s >> x;
  car[0] = 1LL;
  for (int i = 0; i < 64; ++i) {
    long long k = x & (1LL << i), v = s & (1LL << i);
    if (k) {
      long long cr = (v) ? 0 : car[1] * 2;
      long long nocr = (v) ? car[0] * 2 : 0;
      car[0] = nocr;
      car[1] = cr;
    } else {
      long long cr = (v) ? car[1] : car[0];
      long long nocr = (v) ? car[1] : car[0];
      car[0] = nocr;
      car[1] = cr;
    }
  }
  cout << car[0] - ((s == x) ? 2LL : 0) << endl;
  return 0;
}

### Prompt

Generate 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;
long long car[2];
int main() {
  cin >> s >> x;
  car[0] = 1LL;
  for (int i = 0; i < 64; ++i) {
    long long k = x & (1LL << i), v = s & (1LL << i);
    if (k) {
      long long cr = (v) ? 0 : car[1] * 2;
      long long nocr = (v) ? car[0] * 2 : 0;
      car[0] = nocr;
      car[1] = cr;
    } else {
      long long cr = (v) ? car[1] : car[0];
      long long nocr = (v) ? car[1] : car[0];
      car[0] = nocr;
      car[1] = cr;
    }
  }
  cout << car[0] - ((s == x) ? 2LL : 0) << endl;
  return 0;
}

```