// Problem: F. Xorro the Xorman
// Contest: Codeforces - UTPC Contest 10-23-20 Div. 2
// Memory Limit: 256 MB
// Time Limit: 1000 ms
// Date / Time: 2021-10-04 19:35:06
// Author: cosenza
// всё что ни делается - всё к лучшему
// check list -> long long, special cases, array size, mod (a*b%p*c%p not a*b*c%p  ,  (a-b+p)%p not a-b )
//
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//#pragma GCC optimize("Ofast")
//#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//THESE ARE LAST DITCH EFFORTS!!!

#include <bits/stdc++.h>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    long long a, b;
    cin >> a >> b;
    int b1 = 63 - __builtin_clzll(b);
    bool pode = false;
    for(int i = b1; i >= 0; i--) {
        if((a & (1ll << i)) and (b & (1ll << i))) {
            pode = true;
        }
        if(!(a & (1ll << i))) {
            if(b & (1ll << i)) {
                a |= (1ll << i);
            } else {
                if(pode) {
                    a |= (1ll << i);
                }
            }
        }
    }
    cout << a << "\n";
    return 0;
}