#include <bits/stdc++.h>
using std::cin;
using std::cout;
using std::endl;
std::mt19937 rnd(std::chrono::steady_clock::now().time_since_epoch().count());
template <class T> inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T> inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
const int inf = (int)1e9 + 7;
const long long INF = 1LL << 60;

void solve() {
    int A, B;
    cin >> A >> B;
    if (A == 0 or B == 0) {
        cout << 0 << "\n";
        return;
    }
    int msb_a = -1, msb_b = -1;
    {
        for (int i = 0; i < 30; i++) {
            if (A >> i & 1) {
                msb_a = i;
            }
        }

        {
            for (int i = 0; i < 30; i++) {
                if (B >> i & 1) {
                    msb_b = i;
                }
            }
        }
    }
    if (msb_a == msb_b) {
        cout << (1 << msb_a) - 1 << "\n";
    } else {
        cout << (1 << (std::min(msb_a, msb_b) + 1)) - 1 << "\n";
    }
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int I_love_KKT89 = 1;
    // cin >> I_love_KKT89;
    for (int Case = 1; Case <= I_love_KKT89; ++Case) {
        // cout << "Case #" << Case << ": ";
        solve();
    }
    return 0;
}