#include <bits/stdc++.h>
using namespace std;
inline void writeln2() { cout << "\n"; }
inline void writeln() { cout << "\n"; }
inline void readln() {}
template <typename T>
inline void read(T&);
template <typename T>
inline void priws(T);
template <typename T>
inline void print(T);
void err(vector<string>::iterator it) { ++it; }
template <typename Head, typename... Tail>
inline void readln(Head& head, Tail&... tail) {
  read(head);
  readln(tail...);
}
template <typename Head, typename... Tail>
inline void writeln2(Head head, Tail... tail) {
  print(head);
  writeln2(tail...);
}
template <typename Head, typename... Tail>
inline void writeln(Head head, Tail... tail) {
  priws(head);
  writeln2(tail...);
}
template <typename T>
inline void writeln_range(T f, T s) {
  if (f != s)
    for (auto i = f; i != s; ++i) writeln(*i);
}
template <typename Head, typename... Tail>
inline void err(vector<string>::iterator it, Head head, Tail... tail) {
  writeln((*it).substr((*it)[0] == ' '), "=", head);
  err(++it, tail...);
}
vector<string> split(const string& s, char c) {
  vector<string> v;
  stringstream ss(s);
  string x;
  while (getline(ss, x, c)) v.push_back(x);
  return move(v);
}
long long rec(long long s, long long x) {
  int carry = 0;
  for (int j = 60; j >= (int)(0); --j) {
    long long i = 1ll << j;
    if (s & i && x & i && carry == 1) return 0;
    if ((s & i) == 0 && x & i && carry == 0) return 0;
    if (s & i && (x & i) == 0) carry = 1;
    if ((s & i) == 0 && (x & i) == 0) carry = 0;
  }
  return carry == 0 ? (1ll << __builtin_popcountll(x)) - 2 * (s == x) : 0;
}
void run() {
  long long s, x;
  readln(s, x);
  writeln(rec(s, x));
}
int main() {
  ios_base::sync_with_stdio(false);
  run();
  return 0;
}
template <typename T>
inline ostream& operator<<(ostream& os, vector<T>& _a);
template <typename T1, typename T2>
inline istream& operator>>(istream& is, pair<T1, T2>& _a) {
  return is >> _a.first >> _a.second;
}
template <typename T1, typename T2>
inline ostream& operator<<(ostream& os, pair<T1, T2>& _a) {
  return os << _a.first << " " << _a.second;
}
template <typename T>
inline ostream& operator<<(ostream& os, vector<T>& _a) {
  if (_a.size())
    os << _a[0];
  else
    os << "\n";
  for (int i = 1; i < _a.size(); ++i)
    os << "\n "[is_fundamental<T>::value] << _a[i];
  return os;
}
template <typename T>
inline istream& operator>>(istream& is, vector<T>& _a) {
  if (_a.size() == 0) {
    int _n;
    is >> _n;
    _a.resize(_n);
  }
  for (int i = 0; i < _a.size(); ++i) is >> _a[i];
  return is;
}
template <typename T>
inline void print(T _a) {
  cout << " " << _a;
}
template <typename T>
inline void priws(T _a) {
  cout << _a;
}
template <typename T>
inline void read(T& _a) {
  cin >> _a;
}
