#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  long long n;
  cin >> n;
  long long m, k;
  cin >> m >> k;
  long long arr[m];
  for (long long i = 0; i < m; i++) {
    cin >> arr[i];
  }
  long long cnt = 0;
  for (long long i = 0; i < m;) {
    long long cp = (arr[i] - i + k - 1) / k;
    long long j = i + 1;
    while (j < m) {
      long long iskapg = (arr[j] - i + k - 1) / k;
      if (iskapg != cp) {
        break;
      }
      j++;
    }
    cnt++;
    i = j;
  }
  cout << cnt << endl;
}
