#include <bits/stdc++.h>
using namespace std;
const int MX = 2e5 + 9;
const long long inf = (1ll << 60);
const long long mod = 1e9 + 7;
long long s, x, res;
vector<long long> a, b;
int main() {
  cin >> s >> x;
  if (x > s || (s - x) % 2) {
    puts("0");
    return 0;
  }
  for (int i = 0; i <= 50; i++) {
    if (x & (1ll << i)) res++;
  }
  res = (1ll << res) - 2;
  if (x == s) {
    cout << res << endl;
    return 0;
  }
  res += 2;
  long long tmp = s - x;
  tmp /= 2;
  for (int i = 0; i < 50; i++) {
    if ((x & (1ll << i)) && (tmp & (1ll << i))) {
      puts("0");
      return 0;
    }
  }
  cout << res << endl;
}

### Prompt

Please formulate 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;
const int MX = 2e5 + 9;
const long long inf = (1ll << 60);
const long long mod = 1e9 + 7;
long long s, x, res;
vector<long long> a, b;
int main() {
  cin >> s >> x;
  if (x > s || (s - x) % 2) {
    puts("0");
    return 0;
  }
  for (int i = 0; i <= 50; i++) {
    if (x & (1ll << i)) res++;
  }
  res = (1ll << res) - 2;
  if (x == s) {
    cout << res << endl;
    return 0;
  }
  res += 2;
  long long tmp = s - x;
  tmp /= 2;
  for (int i = 0; i < 50; i++) {
    if ((x & (1ll << i)) && (tmp & (1ll << i))) {
      puts("0");
      return 0;
    }
  }
  cout << res << endl;
}

```