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​

using System;

​

public class HelloWorld

{

    public static void Main(string[] args)

    {

        CaculateMoney();

    }

    public static void CaculateMoney () {

        int PRICE_100 = 1000;

        int PRICE_101_150 = 1200;

        int PRICE_151_200 = 2000;

        int PRICE_OVER_200 = 2500;

        int oldNumber;

        int newNumber;

​

        Console.WriteLine ("================= START ===============");

        Console.WriteLine("Enter old number:");

        string userInputOld = Console.ReadLine();

        oldNumber = Convert.ToInt32(userInputOld);

        Console.WriteLine ("Enter new number:");

        string userInputNew = Console.ReadLine();

        newNumber = Convert.ToInt32(userInputNew);

        if (newNumber < oldNumber) {

            Console.WriteLine ("The new number must be greater than the old number!");

            CaculateMoney();

            return;

        } else {

            int diff = newNumber - oldNumber;

            int price = 0;

            if (diff < 100) {

                Console.WriteLine ("Price: " + PRICE_100);

                price = diff * PRICE_100;

            } else if (diff > 100 && diff <= 150) {

                Console.WriteLine ("Price: " + PRICE_101_150);

                price = diff * PRICE_101_150;

            } else if (diff > 150 && diff <= 200) {

                Console.WriteLine ("Price: " + PRICE_151_200);

                price = diff * PRICE_151_200;

            } else {

                Console.WriteLine ("Price: " + PRICE_OVER_200);

                price = diff * PRICE_OVER_200;

            }

            Console.WriteLine ("Your number: " + diff);

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

            Console.WriteLine ("Total money: " + price + "VND");

            CaculateMoney();

            return;

        }

    }

}