#include <bits/stdc++.h>
using namespace std;
int main(void) {
  ios_base ::sync_with_stdio(0);
  long long s, first;
  cin >> s >> first;
  if ((s - first) & 1) return puts("0") * 0;
  long long second = (s - first) / 2;
  int ans = 0;
  for (int i = 0; i < 40; ++i) {
    if (!((second >> i) & 1) && ((first >> i) & 1)) ++ans;
    if (((second >> i) & 1) && ((first >> i) & 1)) return puts("0") * 0;
  }
  return cout << (1ll << ans) - 2 * (s == first) << '\n', 0;
}

### Prompt

Construct a CPP code solution to the problem outlined:

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(void) {
  ios_base ::sync_with_stdio(0);
  long long s, first;
  cin >> s >> first;
  if ((s - first) & 1) return puts("0") * 0;
  long long second = (s - first) / 2;
  int ans = 0;
  for (int i = 0; i < 40; ++i) {
    if (!((second >> i) & 1) && ((first >> i) & 1)) ++ans;
    if (((second >> i) & 1) && ((first >> i) & 1)) return puts("0") * 0;
  }
  return cout << (1ll << ans) - 2 * (s == first) << '\n', 0;
}

```