using System;

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        Array.Sort(a);
        Console.WriteLine("{0:0.00}", (a[1] + a[2] + a[3] + a[4]) / 4d);
    }
}