using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;
using System.IO;

class Program
{
    static int N;
    static long K;
    static int[] L;

    static void Main(string[] args)
    {
        N = int.Parse(Console.ReadLine());
        L = Line().Select(int.Parse).ToArray();
        K = long.Parse(Console.ReadLine());

        double min = 0;
        double max = 1e9;
        for(int i = 0; i < 100; i++)
        {
            double mid = (min + max) / 2.0;
            int cnt = L.Sum(ii => ((int)(ii / mid)));
            if (cnt < K)
            {
                max = mid;
            }
            else
            {
                min = mid;
            }
        }

        Console.WriteLine(max);
    }

    static string[] Line()
    {
        return Console.ReadLine().Split(' ');
    }
}