#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int N;
  cin >> N;
  vector<int> L(N);
  for (int i = 0; i < N; i++) {
    cin >> L[i];
  }
  int64_t K;
  cin >> K;
  auto f = [&](double x) {
    int64_t k = 0;
    for (int i = 0; i < N; i++) {
      k += (int)(L[i] / x);
    }
    return k >= K;
  };
  double lo = 0, hi = *max_element(L.begin(), L.end());
  for (int i = 0; i < 100; i++) {
    double mi = (lo + hi) / 2;
    if (f(mi)) {
      lo = mi;
    } else {
      hi = mi;
    }
  }
  cout << fixed << setprecision(10) << lo << '\n';
  return 0;
}