#include <bits/stdc++.h>
using namespace std;
void printvector(std::vector<long long> v) {
  for (long long i = 0; i < v.size(); ++i) {
    cout << v[i] << " ";
  }
  cout << "" << endl;
}
void printarray(long long a[], long long n) {
  for (long long i = 0; i < n; ++i) {
    cout << a[i] << " ";
  }
  cout << "" << endl;
}
long long f(long long n, long long x) {
  if (n < x) return 0;
  if (n == x) return 1;
  if (x % 2 == 0) {
    long long left = x, right = x;
    long long sum = 0;
    while (left <= n) {
      sum += (right / 2 - left / 2 + 1);
      left = left * 2;
      right = right * 2 + 2;
      right = min(right, n - n % 2);
    }
    left = x + 1, right = x + 1;
    while (left <= n) {
      sum += ((right - left) / 2 + 1);
      left = left * 2 - 1;
      right = right * 2 + 1;
      right = min(right, n - 1 + n % 2);
    }
    return sum;
  } else {
    return 1 + f(n, 2 * x);
  }
}
void solve() {
  long long n, k;
  cin >> n >> k;
  if (k == n) {
    cout << 1 << endl;
    return;
  }
  long long ans1 = 1, ans2 = 0;
  long long l = 2, r = n - n % 2;
  while (l < r) {
    long long mid = 2 * ((l / 2 + r / 2) / 2) + 2;
    long long d = f(n, mid);
    if (d >= k) {
      l = mid;
    } else {
      r = mid - 2;
    }
  }
  ans2 = l;
  l = 1;
  r = n - 1 + n % 2;
  while (l < r) {
    long long mid = 2 * ((l / 2 + r / 2) / 2) + 3;
    long long d = f(n, mid);
    if (d >= k) {
      l = mid;
    } else {
      r = mid - 2;
    }
  }
  ans1 = l;
  cout << max(ans2, ans1) << endl;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
  return 0;
}
