#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 low = 0;
	double high = 1e9;
	for (int t = 0; t < 100; t++)
	{
		double mid = (low + high) / 2;
		long temp = 0;
		for (int i = 0; i < N; i++)
		{
			temp += (long long)(L[i] / mid);
		}
		if (temp >= K) low = mid;
		else high = mid;
	}
	printf("%.14f\n", low);
}