using System;

public class Program

{

    public static void Main()

    {

        int price = 0;    

        Console.WriteLine("(1)紅茶10元、(2)奶茶15元、(3)咖啡20元，請問是否需要購買(y/n)?");

        string ans = Console.ReadLine();

​

        while (ans == "y")

        {        

            Console.WriteLine("請問要喝什麼飲料，紅茶請輸入1、奶茶請輸入2、咖啡請輸入3");

            string a = Console.ReadLine();

            if (a=="1")

            { 

                price = price+10;

            }

            if (a=="2")

            { 

                price = price+15;

            }

            if (a=="3")

            { 

                price = price+20;

            }

            Console.WriteLine("是否還要購買(y/n)?");

            ans = Console.ReadLine();

        }

            Console.WriteLine("總共{0}元",price);

    }

}