using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter 4 numbers to find the mean.");

        ulong f = ulong.Parse(Console.ReadLine());

        ulong s = ulong.Parse(Console.ReadLine());

        ulong t = ulong.Parse(Console.ReadLine());

        ulong fo = ulong.Parse(Console.ReadLine());

        ulong ans = mean(f, s, t, fo);

        Console.WriteLine("The mean of these numbers is " +ans);

    }

    private static ulong mean(ulong f, ulong s, ulong t, ulong fo)

    {

        ulong sum = f+s+t+fo;

        return sum/4;

    }

}