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

#define ll long long
#define rep(i, n) for (int i = 0; i < (n); i++)
#define P pair<int, int>
#define LP pair<ll, ll>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define all(s) s.begin(), s.end()
#define rall(s) s.rbegin(), s.rend()
template<class T>
void chmax(T& a, T b) { a = max(a, b); };
template<class T>
void chmin(T& a, T b) { a = min(a, b); };

int main() {
  int a, b;
  cin >> a >> b;
  auto f = [&](int x) {
    string res;
    while (x) {
      res.pb(x%2+'0');
      x /= 2;
    }
    reverse(all(res));
    return res;
  };
  string sa = f(a);
  string sb = f(b);
  if (sa.size() == sb.size()) {
    int d = sa.size();
    int ans = (1<<(d-1))-1;
    cout << ans << endl;
  } else {
    cout << min(a,b) << endl;
  }
  
  return 0;
}