#include <bits/stdc++.h>
using namespace std;
const int SIZE = 1e5 + 10;
long long n, m, k;
long long a[SIZE];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> m >> k;
  for (long long i = 1; i <= m; i++) cin >> a[i];
  long long cnt = 1, delnums = 0, pag = 1, ans = 0;
  while (pag * k <= n && cnt <= m) {
    if (a[cnt] - delnums > pag * k) {
      pag = (a[cnt] - delnums) / k;
    }
    while (cnt <= m) {
      long long nums = 0;
      if (a[cnt] - delnums > pag * k) break;
      ans++;
      while (a[cnt] - delnums <= pag * k && cnt <= m) cnt++, nums++;
      delnums += nums;
    }
    pag++;
  }
  if (delnums != m) ans++;
  cout << ans << endl;
  return 0;
}
