#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100005;
template <typename T>
void chkmax(T &x, T y) {
  x = max(x, y);
}
template <typename T>
void chkmin(T &x, T y) {
  x = min(x, y);
}
template <typename T>
void read(T &x) {
  x = 0;
  int f = 1;
  char c = getchar();
  for (; !isdigit(c); c = getchar())
    if (c == '-') f = -f;
  for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
  x *= f;
}
template <typename T>
void write(T x) {
  if (x < 0) x = -x, putchar('-');
  if (x > 9) write(x / 10);
  putchar(x % 10 + '0');
}
template <typename T>
void writeln(T x) {
  write(x);
  puts("");
}
int n, m, d, b;
int x[MAXN], y[MAXN];
bool check(int mid) {
  for (int i = 1; i <= n; i++) x[i] = y[i];
  int pos = 1, r = 0;
  for (int i = 1; i <= m; i++) {
    r += 1 + d;
    chkmin(r, n);
    if (i < mid + 1) continue;
    int req = b;
    while (req) {
      if (x[pos]) {
        int used = min(req, x[pos]);
        req -= used;
        x[pos] -= used;
      } else
        pos++;
    }
    if (pos > r) return false;
  }
  int l = n + 1;
  pos = n;
  for (int i = n; i >= m + 1; i--) {
    l -= 1 + d;
    chkmax(l, 1);
    if (i > n - mid) continue;
    int req = b;
    while (req) {
      if (x[pos]) {
        int used = min(req, x[pos]);
        req -= used;
        x[pos] -= used;
      } else
        pos--;
    }
    if (pos < l) return false;
  }
  return true;
}
int main() {
  read(n), read(d), read(b);
  for (int i = 1; i <= n; i++) read(y[i]);
  m = (n + 1) / 2;
  int l = 0, r = n;
  while (l < r) {
    int mid = (l + r) / 2;
    if (check(mid))
      r = mid;
    else
      l = mid + 1;
  }
  writeln(l);
  return 0;
}
