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

int main() {
	int n;
	cin >> n;
	vector<int> l(n);
	for (int i = 0;i < n;i++) {
		cin >> l[i];
	}
	long long k;
	cin >> k;

	double left = 0;
	double right = *max_element(l.begin(), l.end());
	double ans;
	for (int i = 0;i < 100;i++) {
		double mid = (left + right) / 2;
		long long count = 0;
		for (int i = 0;i < n;i++) {
			count += (int)(l[i] / mid);
		}
		if (count >= k) {
			ans = mid;
			left = mid;
		}
		else {
			right = mid;
		}
	}
	cout <<setprecision(15)<< ans << endl;


	return 0;
}