#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
using namespace std;

using ll = long long;
const int INF = 1e9;
const ll inf = 1LL<<62;

void solve() {
  ll a, b; cin >> a >> b;
  ll x = 0, y = 0;
  while ((1LL<<(x+1)) <= a) x++;
  while ((1LL<<(y+1)) <= b) y++;
  if (x != y) cout << min(a, b) << '\n';
  else cout << (1LL<<x)-1 << '\n';
}

int main() {
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  // int t; cin >> t;
  /*while (t--)*/ solve();
}