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

int main() {
    long long a, c;
    cin >> a >> c;
    if (a > c) swap(a, c);

    long long val = 63 - __builtin_clzll(c);  // Faster than log2()
    long long ans = (1LL << val) - 1;         // Directly compute ans
    cout << min(ans, a) << '\n';              // Minimize operations

    return 0;
}