#include <bits/stdc++.h>

using std::cin;
using std::cout;
using std::min;

int main() {
    int a, b;
    cin >> a >> b;
    
    if (a < b) std::swap(a, b);
    
    int x = 1;
    while (x*2 <= a) x *= 2;
    
    int ans = min(x-1, b);
    cout << ans << '\n';
    
    return 0;
}