#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int s, x;
  cin >> s >> x;
  long long int e = 0;
  bool ok = true;
  int c[2][2] = {};
  for (int i = 0; i < 50; i++) {
    bool si = s & (1LL << i), xi = x & (1LL << i);
    if (si == 0 && xi == 0) ok &= e <= 1, e = 1;
    if (si == 0 && xi == 1) ok &= e > 0, e = 2;
    if (si == 1 && xi == 0) ok &= e > 0, e = 1;
    if (si == 1 && xi == 1) ok &= e <= 1, e = 0;
    c[si][xi]++;
  }
  long long int ans = 0;
  if (ok) {
    ans = (1LL << (c[0][1] + c[1][1]));
    ans -= (s == x) * 2;
  }
  cout << max(ans, 0LL) << "\n";
  return 0;
}

### Prompt

Please create a solution in CPP 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 main() {
  long long int s, x;
  cin >> s >> x;
  long long int e = 0;
  bool ok = true;
  int c[2][2] = {};
  for (int i = 0; i < 50; i++) {
    bool si = s & (1LL << i), xi = x & (1LL << i);
    if (si == 0 && xi == 0) ok &= e <= 1, e = 1;
    if (si == 0 && xi == 1) ok &= e > 0, e = 2;
    if (si == 1 && xi == 0) ok &= e > 0, e = 1;
    if (si == 1 && xi == 1) ok &= e <= 1, e = 0;
    c[si][xi]++;
  }
  long long int ans = 0;
  if (ok) {
    ans = (1LL << (c[0][1] + c[1][1]));
    ans -= (s == x) * 2;
  }
  cout << max(ans, 0LL) << "\n";
  return 0;
}

```