#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n, m, k;
  cin >> n >> m >> k;
  long long arr[m + 1];
  for (int i = 1; i <= m; ++i) {
    cin >> arr[i];
  }
  long long level = 1;
  long long rem = 0;
  long long ops = 0;
  int i = 1;
  long long extra = 0;
  while (rem < m) {
    extra = 0;
    while (i <= m && arr[i] <= (level * k + rem)) {
      i++;
      extra++;
    }
    rem += extra;
    if (extra > 0) {
      ops++;
    }
    if (i >= m + 1) {
      break;
    }
    level += ceil((double)(arr[i] - (level * k + rem)) / k);
  }
  cout << ops;
}
