#include <bits/stdc++.h>
#pragma GCC optimize(2)
using namespace std;
const int INF = 1e9 + 7;
const int N = 2e5 + 7;
const int M = 5e6 + 7;
int num[N];
signed main() {
  ios::sync_with_stdio(false);
  int n, d, b, A, B, sum;
  cin >> n >> d >> b;
  for (int i = 1; i <= n; i++) cin >> num[i];
  A = sum = 0;
  for (int i = 1, j = 1; i <= n + 1 >> 1; i++) {
    for (; j <= min(i * (d + 1), n); j++) sum += num[j];
    if (sum < b)
      A++;
    else
      sum -= b;
  }
  reverse(num + 1, num + n + 1);
  B = sum = 0;
  for (int i = 1, j = 1; i <= n / 2; i++) {
    for (; j <= min(i * (d + 1), n); j++) sum += num[j];
    if (sum < b)
      B++;
    else
      sum -= b;
  }
  cout << max(A, B) << "\n";
  return 0;
}
