#include <bits/stdc++.h>
using namespace std;

template <typename T, typename U> void cmin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U> void cmax(T &a, U b) {
  if (a < b) a = b;
}

signed main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  long N;
  cin >> N;
  vector<long> L(N);
  for (long i = 0; i < N; i++) cin >> L.at(i);
  long K;
  cin >> K;

  auto f = [&](long double mid) {
    long tmp = 0;
    for (auto l : L) tmp += long(l / mid);
    if (tmp >= K) return true;
    else return false;
  };

  long double ok = 1e-10, ng = 1e10 + 1e-10;
  for (long i = 300; i; i--) {
    long double mid = (ok + ng) / 2;
    (f(mid)) ? ok = mid : ng = mid;
  }
  cout << fixed << setprecision(9) << ok << "\n";
}