#include <bits/stdc++.h>

using namespace std;

typedef long long int ll;
typedef pair<ll, ll> pll;

#define FOR(i, n, m) for(ll (i)=(m);(i)<(n);++(i))
#define REP(i, n) FOR(i,n,0)
#define OF64 std::setprecision(10)

const ll MOD = 1000000007;
const ll INF = (ll) 1e15;

int main() {
    ll A, B;
    cin >> A >> B;
    ll n = 0;
    REP(i, 40) {
        ll a = ((A >> i) & 1);
        ll b = ((B >> i) & 1);

        if (a == 1 && b == 0) {
            cout << 0 << endl;
            return 0;
        }
        if (a != b)
            n++;
    }
    ll p = pow(2LL, n - 1);
    if (n == 0)
        cout << 1 << endl;
    else
        cout << p << endl;
    return 0;
}