#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

int main(){

    ll A, B;
    cin >> A >> B;
    if (A > B) swap(A, B);
    for (int i=30; i>=0; i--){
        if ((A & 1LL<<i) && (B & 1LL<<i)){
            cout << (1LL<<i)-1 << endl;
            return 0;
        }
        else if (B & 1LL<<i){
            cout << A << endl;
            return 0;
        }
    }

    return 0;
}