#include <bits/stdc++.h>

#define REP(i, x, n) for(int i = x; i < (int)(n); i++)
#define rep(i, n) REP(i, 0, n)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define F first
#define S second
#define mp make_pair

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;

int main() {
  // ios_base::sync_with_stdio(false);
  int N;
  cin >> N;
  vector<double> L(N);
  rep(i, N) cin >> L[i];
  ll K;
  cin >> K;

  double lb = 0;
  double ub = 1e10;

  rep(i, 100) {
    double mid = (lb + ub) / 2;
    ll cnt = 0;
    rep(j, N) {
      cnt += (ll)(L[j] / mid);
      if(cnt >= K) break;
    }
    if(cnt >= K) lb = mid;
    else ub = mid;
  }

  printf("%.10f\n", lb);
  
  return 0;
}