using System;
using System.Collections.Generic;
using System.Linq;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] x = Console.ReadLine().Split().Select(int.Parse).ToArray();
            Console.WriteLine(((x.Sum() - x.Max() - x.Min()) / 4).ToString("F2"));
        }
    }
}