#include<bits/stdc++.h>
using namespace std;

int main(){
    int64_t A, B; cin >> A >> B;
    int64_t a = 1, b = 1;
    while(A >= a * 2) a <<= 1;
    while(B >= b * 2) b <<= 1;
    if(a == b){
        cout << a - 1 << '\n';
        return 0;
    }
    if(a < b){
        swap(a, b);
        swap(A, B);
    }
    cout << B << '\n';
}