#include <bits/stdc++.h>
using namespace std;
int main() {
  long long a, b;
  cin >> a >> b;
  long long ans = 0;
  while (ans * 2  + 1 <= min(a, b)) {
    ans = ans * 2 + 1;
  }
  cout << ans << endl;
  return 0;
}