#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long s, x;
  cin >> s >> x;
  s -= x;
  if (s % 2 || s < 0) {
    cout << 0 << '\n';
    return 0;
  }
  s >>= 1;
  bool ok = true;
  for (int i = 50; i >= 0; --i)
    if (s & (1LL << i)) ok &= (~x & (1LL << i)) != 0;
  if (!ok) {
    cout << 0 << '\n';
    return 0;
  }
  long long ans = 1LL << __builtin_popcountll(x);
  cout << (s == 0 ? ans - 2 : ans) << '\n';
}

### 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;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long s, x;
  cin >> s >> x;
  s -= x;
  if (s % 2 || s < 0) {
    cout << 0 << '\n';
    return 0;
  }
  s >>= 1;
  bool ok = true;
  for (int i = 50; i >= 0; --i)
    if (s & (1LL << i)) ok &= (~x & (1LL << i)) != 0;
  if (!ok) {
    cout << 0 << '\n';
    return 0;
  }
  long long ans = 1LL << __builtin_popcountll(x);
  cout << (s == 0 ? ans - 2 : ans) << '\n';
}

```