#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>
#include <algorithm>
#include <functional>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cctype>
#include <string>
#include <cstring>

using namespace std;

typedef long long ll;

int n;
double *len;
ll k;
bool check(double x) {
  ll cnt = 0;
  for (int i = 0; i < n; i++) {
    cnt += floor(len[i]/x);
    if (cnt >= k) return true;
  }

  return false;
}

int main() {
  cin >> n;
  len = new double[n];
  for (int i = 0; i < n; i++) cin >> len[i];
  cin >> k;

  double l, r;
  l = 0; r = 1e10;
  while (abs(l-r) >= 1e-10) {
    double p = (l+r)/2;
    if (!check(p)) {
      r = p;
    }else {
      l = p;
    }
  }

  printf ("%.10f\n", l);
}