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

#define double long double

using ll = long long;
using VB = vector<bool>;
using VVB = vector<VB>;
using VC = vector<char>;
using VI = vector<int>;
using VVI = vector<VI>;
using VVVI = vector<VVI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using VVVL = vector<VVL>;
using VVVVL = vector<VVVL>;
using VD = vector<double>;
using VVD = vector<VD>;
using VVVD = vector<VVD>;
using P = pair<int, int>;

#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, a, b) for (ll i = a; i < (ll)(b); i++)
#define ALL(a) (a).begin(),(a).end()

constexpr int INF = 1001001001;
constexpr ll LINF = 2001001001001001001ll;
constexpr int DX[] = {1, 0, -1, 0};
constexpr int DY[] = {0, 1, 0, -1};

template< typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true); }
template< typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true); }

const ll MOD = 1000000007;

int main() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int A, B, X = 1;
    cin >> A >> B;
    if (A > B) swap(A, B);
    while (X * 2 <= B) X *= 2;
    cout << min(X - 1, B - X + A) << endl;
}