#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long n, m, k;
  cin >> n >> m >> k;
  long long p[m];
  for (long long int i = 0; i < m; i++) cin >> p[i];
  sort(p, p + m);
  long long an = 0, x = 0, c = 0, cp = 1;
  while (1) {
    long long y = x, pg = ceil((long double)(p[x] - x) / (k));
    while (y < m && ceil((long double)(p[y] - x) / (k)) == pg) y++;
    if (y == m) {
      cout << an + 1;
      return;
    }
    an++;
    x = y;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long TESTS = 1;
  while (TESTS--) {
    solve();
  }
  return 0;
}
