#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
long long n, k;
int main() {
  cin >> n >> k;
  long long now = n, cnt = 1, a = 1, b = (n & 1) ? 2 : 1, c = (n & 1) ? 1 : 2,
            d = (n & 1) ? 2 : 1;
  if (n == k) return puts("1"), 0;
  while (1) {
    if (a >= k) {
      cout << now << '\n';
      return 0;
    }
    if (b >= k) {
      cout << now - 1ll << '\n';
      return 0;
    }
    if (c >= k) {
      cout << now - 2ll << '\n';
      return 0;
    }
    if (d >= k) {
      cout << now - 3ll << '\n';
      return 0;
    }
    if (now & 1ll) {
      now >>= 1ll;
      if (now & 1ll) {
        a = b + 1ll;
      } else {
        a = b + (1ll << cnt);
      }
    } else {
      now >>= 1ll;
      if (now & 1ll) {
        a++;
      } else {
        a = a + (1ll << cnt);
      }
    }
    cnt++;
    b = (now & 1ll) ? a + ((1ll << cnt) - 1ll) : ((1ll << cnt) - 1ll);
    c = (now & 1ll) ? ((1ll << cnt) - 1ll) : ((1ll << cnt) - 1ll) << 1ll;
    if (now == 6)
      d = a + 1;
    else if (now == 5)
      d = b + c + 1;
    else if (now == 4)
      d = n;
    else {
      d = (now & 1ll) ? c + 1 + ((1ll << (cnt - 1)) - 1ll) * 2
                      : (1ll << cnt) - 1ll;
    }
  }
}
