#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
long long n, d, c;
long long a[N], b[N];
bool check(long long x);
int main() {
  cin >> n >> d >> c;
  for (int i = 1; i <= n; ++i) {
    cin >> a[i];
  }
  int l = 0, r = (n + 1) / 2 - 1;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (check(mid)) {
      r = mid - 1;
    } else {
      l = mid + 1;
    }
  }
  cout << r + 1;
}
bool check(long long x) {
  for (int i = 1; i <= n; ++i) {
    b[i] = a[i];
  }
  long long f = (n + 1) / 2;
  long long l = x + 1, r = f, t = l, p = 1;
  for (int i = l; i <= r; ++i, ++t) {
    long long temp = c;
    while (temp) {
      if (p > n) {
        return false;
      } else if (!b[p]) {
        ++p;
      } else if (p - d * t > i or p + d * t < i) {
        return false;
      } else if (b[p] >= temp) {
        b[p] -= temp;
        temp = 0;
      } else {
        temp -= b[p];
        b[p] = 0;
      }
    }
  }
  l = f + 1;
  r = n - x;
  t = n - r + 1;
  p = n;
  for (int i = r; i >= l; --i, ++t) {
    long long temp = c;
    while (temp) {
      if (p < 1) {
        return false;
      } else if (!b[p]) {
        --p;
      } else if (p - d * t > i or p + d * t < i) {
        return false;
      } else if (b[p] >= temp) {
        b[p] -= temp;
        temp = 0;
      } else {
        temp -= b[p];
        b[p] = 0;
      }
    }
  }
  return true;
}
