#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()
{
	int n;
	cin >> n;
	vector<ll> values(n);
	for(int i = 0; i < n;i++)
	{
		cin >> values[i];
	}
	int k;
	cin >> k;
	
	double minValue = 0;
	double maxValue = 1e9;
	for(int i = 0; i < 100;i++)
	{
		double mid = (minValue + maxValue)/2.0;
        long 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);
}