using System;

public class Program

{

    public static void Main()

    {

        int a,q=0;

        double  p=0;

        string s;

        do {

            Console.Write("a=");

            s=Console.ReadLine();

            a=Convert.ToInt32(s);

            p+=a;

            q++;

        }

        while (a!=0);

        p=p/(q-1);

        Console.WriteLine("p="+p);

    }

}