#region ZIPPER
using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
using System.Numerics;
using sc = Scanner;
class Program
{
    static void Main(string[] args)
    {
        Solver solver = new Solver();
        solver.Solve();
#if DEBUG
        System.Console.WriteLine("続行するには何かキーを押してください．．．");
        System.Console.ReadKey();
#endif

    }
}
/// <summary>
/// Java風のスキャナー，自作（某最速の人を参考） 自分の実装のせいか，バグってるっぽい バグが出たらO(n^3) n=100000 でTLE
/// </summary>
public static class Scanner
{
    public static string NextString()
    {
        string tmp = "";
        while (true)
        {
            int readData;
            string data;
            readData = Console.Read();
            if (readData == -1) //EOF
            {
                break;
            }
            data = char.ConvertFromUtf32(readData);
            if (data == " " || data == "\n")
            {
                break;
            }
            tmp += data;
        }
        return tmp;
    }
    public static int NextInt()
    {
        string tmp = "";
        while (true)
        {
            int readData;
            string data;
            readData = Console.Read();
            if (readData == -1) //EOF
            {
                break;
            }
            data = char.ConvertFromUtf32(readData);
            if (data == " " || data == "\n")
            {
                break;
            }
            tmp += data;
        }
        return int.Parse(tmp);
    }
    public static long NextLong()
    {
        string tmp = "";
        while (true)
        {
            int readData;
            string data;
            readData = Console.Read();
            if (readData == -1) //EOF
            {
                break;
            }
            data = char.ConvertFromUtf32(readData);
            if (data == " " || data == "\n")
            {
                break;
            }
            tmp += data;
        }
        return long.Parse(tmp);
    }
    public static double NextDouble()
    {
        string tmp = "";
        while (true)
        {
            int readData;
            string data;
            readData = Console.Read();
            if (readData == -1) //EOF
            {
                break;
            }
            data = char.ConvertFromUtf32(readData);
            if (data == " " || data == "\n")
            {
                break;
            }
            tmp += data;
        }
        return double.Parse(tmp);
    }

    public static string[] NextStrArray()
    {
        return Console.ReadLine().Split(' ');
    }
    public static int[] NextIntArray()
    {

        string[] s = NextStrArray();
        int[] a = new int[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = int.Parse(s[i]);
        }
        return a;
    }
    public static long[] NextLongArray()
    {
        string[] s = NextStrArray();
        long[] a = new long[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = long.Parse(s[i]);
        }
        return a;
    }
    public static double[] NextDoubleArray()
    {
        string[] s = NextStrArray();
        double[] a = new double[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = double.Parse(s[i]);
        }
        return a;
    }
}
#endregion ZIPPER

public class Solver
{
#region IGNORE_ME
    public Solver()
    {
        //こんすとらくたん　きにしなくてよろしい
    }
#endregion IGNORE_ME

#region FIELD

#endregion FIELD

    public void Solve()
    {
        int n = sc.NextInt();
        int[] l = sc.NextIntArray();
        int k = sc.NextInt();
        double eps = 1.0/1000000000000000;
        double low = 0;
        double mid = 0;
        double hi = 2 * 10000 + 1000; // seiyaku ni yoru max yori tyotto over
        while (hi - low > eps)
        {
            mid = (low + hi) / 2;
            if (canCut(l,mid,k))
            {
                low = mid;
            }
            else
            {
                hi = mid;
            }
        
        }
        Console.WriteLine((low+hi)/2);
#if DEBUG
        Console.WriteLine("");//local check
#endif
    }
    /// <summary>
    ///ipponnatari s no nagasa de k hon kiretu
    /// </summary>
    /// <param name="l"></param>
    /// <param name="s"></param>
    /// <returns></returns>
    bool canCut(int[] l,double s, int k)
    {
        int countOfCut = 0;
        for (int i = 0; i < l.Length; i++)
        {
            countOfCut += (int)(l[i]/s);
        }
        return countOfCut >= k ? true : false;
    }

}