using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace yukicoderTest
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            int[] num = new int[input.Length];
            double total = 0;
            for(int i=0;i<input.Length;i++)
            {
                num[i] = int.Parse(input[i]);
            }
            Array.Sort(num);
            for(int i=1;i<num.Length-1;i++)
            {
                total = total + num[i];
            }
            total = total / 4;
            if(total%1==0)
            {
                Console.WriteLine(total + ".00");
            }
            else
            {
                string tmp = total.ToString();
                int point = tmp.IndexOf(".", 0);
                if (tmp.Length >= 6)
                {
                    Console.WriteLine(total = int.Parse(tmp.Remove(point + 2, tmp.Length - 1)));
                }
                else
                {
                    Console.WriteLine(total);
                }
            }
        }

    }
}