#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
    ll A, B;
    cin >> A >> B;
    ll t = 1;
    ll ans = 0;
    for (int i = 0; i < 31; i++) {
        ll u = A & t;
        ll v = B & t;
        if (u != 0 && v == 0) {
            cout << 0 << "\n";
            return 0;
        } else if (u == 0 && v != 0) {
            //cout << u << " " << v << "\n";
            ans++;
        }
        t *= 2;
    }
    ans = max(ans, 1ll);
    cout << (1<<(ans - 1)) << "\n";
    return 0;
}