#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;

//#define DISABLE_PRINT

#if defined(ENABLE_PRINT) && !defined(DISABLE_PRINT)

#define P(...) fprintf(stderr, __VA_ARGS__)
#define P2(fmt) fprintf(stderr, fmt)
#define LP fprintf(stderr, "L: %d\n", __LINE__)

#else

#define P(...) ((void)0)
#define P2(fmt) ((void)0)
#define LP ((void)0)

#endif

#define rep(i, n) for(int i = 0; i < (int)(n); ++i)
#define ALL(x) x.begin(),x.end()

using ll = long long;
using ull = unsigned long long;

int main(int, const char**)
{
    array<int, 2> V; cin >> V[0] >> V[1];
    sort(ALL(V));
    auto f = [](int x) {
        int ans = 0;
        while(x != 0) {
            x /= 2;
            ans++;
        }
        return ans;
    };

    auto f0 = f(V[0]);
    auto f1 = f(V[1]);
    if(f1 > f0) {
        cout << V[0] << endl;
        return 0;
    }
    
    auto ans = (1 << (f0 - 1)) - 1;
    cout << ans << endl;
    return 0;
}