#include <bits/stdc++.h>
using namespace std;
void testCase() {}
int a[1000000];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, d, b;
  cin >> n >> d >> b;
  for (int i = 0; i < n; i++) cin >> a[i];
  int x1 = 0;
  int ind = -1;
  long long sum = 0;
  for (int i = 0; i < (n + 1) / 2; i++) {
    for (int j = 0; j < d + 1; j++) {
      if (ind == n - 1) break;
      ind++;
      sum += a[ind];
    }
    if (sum >= b)
      sum -= b;
    else
      x1++;
  }
  reverse(a, a + n);
  int x2 = 0;
  ind = -1;
  sum = 0;
  for (int i = 0; i < n / 2; i++) {
    for (int j = 0; j < d + 1; j++) {
      if (ind == n - 1) break;
      ind++;
      sum += a[ind];
    }
    if (sum >= b)
      sum -= b;
    else
      x2++;
  }
  cout << max(x1, x2) << "\n";
}
