#include <bits/stdc++.h>
using namespace std;
inline int _lg(long long x) { return 63 - __builtin_clzll(x); }
long long n, k, ans;
inline long long calc(long long x) {
  if (x <= 0 || x > n) return 0;
  int bn = _lg(n);
  int bx = _lg(x);
  long long o = x - (n >> (bn - bx)), num = 0;
  if (o > 0)
    num = (1ll << (bn - bx)) - 1;
  else if (o < 0)
    num = (2ll << (bn - bx)) - 1;
  else
    num = (n & ((1ll << (bn - bx)) - 1)) + (1ll << (bn - bx));
  if (x % 2 == 0) num += calc(x + 1);
  return num;
}
inline void upd(long long x) {
  long long cnt = calc(x);
  if (cnt >= k && x >= ans) ans = x;
}
int main() {
  scanf("%lld%lld", &n, &k);
  for (int i = 1; i <= (100); ++i) upd(i);
  for (int i = 0; i <= (61); ++i)
    upd((1ll << i) - 1), upd((1ll << i) - 2), upd((1ll << i) - 3);
  long long m = n;
  while (m)
    upd(m + 3), upd(m + 2), upd(m + 1), upd(m), upd(m - 1), upd(m - 2),
        upd(m - 3), m >>= 1;
  printf("%lld\n", ans);
  return 0;
}
