/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2022.05.28 00:59:29
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;


int main() {
    int a,b;cin >> a >> b;
    int _a = a;
    int _b = b;
    int c = 0;
    while(_a > 1 && _b > 1) {
        c++;
        _a /= 2;
        _b /= 2;
    }
    if (_a==_b && _b == 1) {
        cout << (1<<c)-1 << endl;
    }
    else if (_a == 1) {
        cout << a << endl;
    }
    else {
        cout << b << endl;
    }
    return 0;
}