#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <map>
#include <vector>
#include <memory.h>

using namespace std;
typedef signed long long ll;

int main()
{
	ll n;
	cin >> n;
	vector<ll> values(n);
	for(int i = 0; i < n;i++)
	{
		cin >> values[i];
	}
	ll k;
	cin >> k;
	
	double minValue = 0;
	double maxValue = 1e9;
	for(int i = 0; i < 100;i++)
	{
		double mid = (minValue + maxValue)/2.0;
		ll sum = 0;
		for (int i = 0; i < n; i++)
		{
			sum += (ll)(values[i]/mid);
		}
		if (sum >= k)
		{
			minValue = mid;
		}
		else
		{
			maxValue = mid;
		}
	}
	printf("%.15f\n", minValue);
}