#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
const long long N = 1e6 + 10;
const long double eps = 1e-9;
const long long inf = 1e18;
long long a[N], b[N], c[N], d[N];
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n, k;
  long long m;
  cin >> n >> m >> k;
  long long a[m];
  for (long long i = 0; i < m; ++i) cin >> a[i];
  long long s = 0, i = 0, j = 0, k1 = k;
  while (j < m) {
    while (a[j] <= k1 + i) j++;
    if (i == j) {
      s--;
      k1 = ((a[j] - i) / k) * k;
      if ((a[j] - i) % k) k1 += k;
    }
    i = j;
    s++;
  }
  cout << s;
  return 0;
}
