#include <bits/stdc++.h>
using namespace std;
int cek[27];
int main() {
  int n, k;
  string kata;
  cin >> n >> k;
  cin >> kata;
  for (int i = 0; i < n; i++) cek[kata[i] - 'a']++;
  int nilai[n];
  for (int i = 'b'; i <= 'z'; i++) cek[i - 'a'] += cek[i - 'a' - 1];
  for (int i = n - 1; i >= 0; i--) {
    nilai[i] = cek[kata[i] - 'a'];
    cek[kata[i] - 'a']--;
  }
  for (int i = 0; i < n; i++)
    if (nilai[i] > k) cout << kata[i];
  return 0;
}
