#include <bits/stdc++.h>
using namespace std;
int dr[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dc[] = {0, -1, 0, 1, -1, 1, -1, 1};
const int MAX = 1e4 + 7;
const int MOD = 1e9 + 7;
int main() {
  long long s, x, ans = 1, r;
  cin >> s >> x;
  if ((s - x) % 2 != 0 || (s - x) / 2 < 0) return (cout << "0\n", 0);
  r = (s - x) / 2;
  if (s - x == 0)
    s = -2;
  else
    s = 0;
  while (x) {
    int br = r % 2;
    r /= 2;
    int bx = x % 2;
    x /= 2;
    if (bx == 0) continue;
    if (bx && br) return (cout << "0\n", 0);
    ans *= 2;
  }
  cout << ans + s << "\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 dr[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dc[] = {0, -1, 0, 1, -1, 1, -1, 1};
const int MAX = 1e4 + 7;
const int MOD = 1e9 + 7;
int main() {
  long long s, x, ans = 1, r;
  cin >> s >> x;
  if ((s - x) % 2 != 0 || (s - x) / 2 < 0) return (cout << "0\n", 0);
  r = (s - x) / 2;
  if (s - x == 0)
    s = -2;
  else
    s = 0;
  while (x) {
    int br = r % 2;
    r /= 2;
    int bx = x % 2;
    x /= 2;
    if (bx == 0) continue;
    if (bx && br) return (cout << "0\n", 0);
    ans *= 2;
  }
  cout << ans + s << "\n";
}

```