#include <bits/stdc++.h>
using namespace std;
long long N, K;
long long Top, Bot, H[200005], cnt[200005];
long long hcnt[200005];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> N >> K;
  Top = 0, Bot = 2e5;
  for (int i = 0; i <= N - 1; i++) {
    cin >> H[i];
    cnt[H[i]]++;
    Top = max(Top, H[i]);
    Bot = min(Bot, H[i]);
  }
  long long curc = 0;
  for (int i = Top; i >= 1; i--) {
    curc += cnt[i];
    hcnt[i] += curc;
  }
  long long cutt = 0;
  int ans = 0;
  for (int i = Top; i >= Bot + 1; i--) {
    if (cutt + hcnt[i] > K) {
      ans++;
      cutt = hcnt[i];
    } else
      cutt += hcnt[i];
  }
  if (cutt) ans++;
  cout << ans << '\n';
  return 0;
}
