#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++;
    }

    cout << pow(2, n - 1) << endl;
    return 0;
}