using System;

public class Program

{

    public static void Main()

    {

​

double S, O, H, A;

S = double.Parse(Console.ReadLine());

Console.WriteLine();

O = double.Parse(Console.ReadLine());

Console.WriteLine();

​

H = double.Parse(Console.ReadLine());

Console.WriteLine();

​

        A = (S + O + H) / 3;

        Console.WriteLine(A);

    }

}