#include <bits/stdc++.h>
using namespace std;
const int P = 1e9 + 7;
int add(int a, int b) {
  if ((a += b) >= P) a -= P;
  return a;
}
int sub(int a, int b) {
  if ((a -= b) < 0) a += P;
  return a;
}
int mul(int a, int b) { return 1ll * a * b % P; }
int kpow(int a, int b) {
  int r = 1;
  for (; b; b >>= 1, a = mul(a, a)) {
    if (b & 1) r = mul(r, a);
  }
  return r;
}
const int N = 1e5 + 7;
long long n, d, b, a[N], s[N], pr, pl, ans1, ans2, suml, sumr, usel, user;
int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  cin >> n >> d >> b;
  for (int i = (1); i < (n + 1); i++) cin >> a[i], s[i] = s[i - 1] + a[i];
  for (int t = (1); t < (n / 2 + 1); t++) {
    pr = min(n, t * d + t);
    pl = max(1ll, n - t + 1 - t * d);
    suml = s[pr] - s[0];
    sumr = s[n] - s[pl - 1];
    if (suml - usel >= b)
      usel += b;
    else
      ans1++;
    if (sumr - user >= b)
      user += b;
    else
      ans2++;
  }
  cout << max(ans1, ans2);
  return 0;
}
