#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  ll n, m, k;
  cin >> n >> m >> k;
  vector<ll> vec(m);
  for (ll &v : vec) cin >> v;
  ll ans = 0, i = 0;
  while (i < m) {
    ll t = (vec[i] - i - 1) / k, j = i + 1;
    while (j < m && (vec[j] - i - 1) / k == t) j++;
    ans++, i = j;
  }
  cout << ans;
  return 0;
}
