using System;

​

public class Program

{

    public static void Main()

    {

        int sum = 0;

        int num = 1;

        int count = 0;

        while (num > 0)

        {

            num = int.Parse(Console.ReadLine());

            if (num > 0)

                sum += num;

                count++;

        }

​

        Console.WriteLine(sum * 1.0 / count);

    }

}