import java.util.Scanner;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author SHON
 */
public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
            System.out.println("To finish, please type 'n'");
            System.out.println("Plese input a mark.");

            Scanner s = new Scanner(System.in);
            while (true)
            {
                avergaeCalculation();

                System.out.println("Do you wish to continue? (y/n)");

                String str = s.next();
                if (str != null && str != "y")
                {
                    break;
                }
            }



            //Console.ReadLine();
    }

    private static void avergaeCalculation()
        {
            Scanner s = new Scanner(System.in);

            int[] arr = {};

            while (true)
            {
                // Ask user for the number

                String str = s.next();
                if (str != null && "n".equals(str))
                {
                    break;
                }
/**/
                int mark = 0 ;//= s.nextInt();


                // Make sure that the mark is a number


                while (true)
                {
                    try
                    {
                        mark = Integer.parseInt(str);
                        break;
                    }
                    catch(NumberFormatException e)
                    {
                        System.out.println("Your input is invalid! Please enter a mark.");
                        str = s.next();
                    }
                }


                // Accumlate the marks

                // Add



                arr = addMark(arr, mark);

                // Ask the user if they want to continue
            }

            // Divide the count and accumulated marks
            int count = arr.length;

            int markSum = 0;

            for(int i = 0; i < arr.length; i++)
            {
                markSum += arr[i];
            }

            double average = count > 0 ? (double)markSum / count : 0.0;

            System.out.println(String.format("Your average mark is: %1$,.2f", average));
        }

        private static int[] addMark(int[] arr, int mark)
        {
            int[] temp = arr != null ? new int[arr.length + 1] : new int[1];

            Copy(arr, temp);

            temp[temp.length - 1] = mark;

            return temp;
        }

        private static void Copy(int[] source, int[] target)
        {
            if (source == null || target == null)
            {
                return;
            }

            for (int i = 0; i < source.length && i < target.length; i++)
            {
                target[i] = source[i];
            }
        }

}