using System;

public class Program

{

    public static void Main()

    {

        int coffeecost=0;

        start:

        Console.WriteLine("please select size:1. small 2. medium 3. large");

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

        switch (userchoice)

        {

            case 1:

            coffeecost +=1;

            break;

            case 2:

            coffeecost +=2;

            break;

            case 3:

            coffeecost +=3;

            break;

            default:

            Console.WriteLine("you choice {0} is not valid ",userchoice);

            goto start;

        }

        decide:

        Console.WriteLine("Do you need one more coffee - yes or no ?");

        string userdecision = Console.ReadLine();

        switch(userdecision.ToUpper())

        {

         case "YES":

            goto start;

        case "NO":

            break;

        default:

            Console.WriteLine("you desicion {0} is invalide.please try again..",userdecision);

            goto decide;

        }

        Console.WriteLine("Thank you for shopping with us.");

        Console.WriteLine("your total bill is = {0}$",coffeecost);

​

    }

}