#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	cin >> n;
	vector<double> L(n);
	for (int i = 0; i < n; i++) cin >> L[i];
	ll K;
	cin >> K;
	double ok = 0, ng = 1e9 + 1;
	for (int i = 0; i < 100; i++) {
		double mid = (ok + ng) / 2;
		ll cnt = 0;
		for (int j = 0; j < n; j++) {
			cnt += (ll)(L[j] / mid);
		}
		if (cnt >= K) ok = mid;
		else ng = mid;
	}
	cout << fixed << setprecision(10) << ok << endl;
	return 0;
}