#include <bits/stdc++.h>
using namespace std;
template <class X>
bool mini(X& a, const X& b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class X>
bool maxi(X& a, const X& b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
typedef const int& ci;
long long s, x;
void enter() { cin >> s >> x; }
void solve() {
  long long a = (s - x) >> 1;
  if ((s & 1) != (x & 1) || s < x || (a & x)) return void(cout << 0);
  int cnt = 0;
  for (int i = 60, _b = (0) - 1; i > _b; --i)
    if (!(a >> i & 1) && (x >> i & 1)) ++cnt;
  cout << max(0ll, (1ll << cnt) - (!a ? 2 : 0));
}
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(0);
  enter();
  solve();
}

### Prompt

Generate 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;
template <class X>
bool mini(X& a, const X& b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class X>
bool maxi(X& a, const X& b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
typedef const int& ci;
long long s, x;
void enter() { cin >> s >> x; }
void solve() {
  long long a = (s - x) >> 1;
  if ((s & 1) != (x & 1) || s < x || (a & x)) return void(cout << 0);
  int cnt = 0;
  for (int i = 60, _b = (0) - 1; i > _b; --i)
    if (!(a >> i & 1) && (x >> i & 1)) ++cnt;
  cout << max(0ll, (1ll << cnt) - (!a ? 2 : 0));
}
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(0);
  enter();
  solve();
}

```