#include <iostream>
#include <cmath>
#include <vector>
#include <iomanip>
#include <algorithm>

using namespace std;

const double EPS = 1E-10;

int main() {
	int n;
	cin >> n;
	vector<double> l(n);
	for (int i = 0; i < n; ++i) {
		cin >> l[i];
	}
	long long k;
	cin >> k;
	double lower = 0, upper = *max_element(l.begin(), l.end());
	double preLength = 0.0;
	while (upper - lower > EPS || (upper - lower) / lower > EPS) {
		double length = (lower + upper) / 2.;
		if (length == preLength) {
			break;
		}
		preLength = length;
		long long count = 0;
		for (int i = 0; i < n; ++i) {
			count += (long long)floor(l[i] / length);
		}
		if (count >= k) {
			lower = length;
		} else {
			upper = length;
		}
	}
	cout << fixed << setprecision(20) << lower << endl;
	return 0;
}