using System;

public class Program

{

​

    public static void Main()

    {

        Console.WriteLine(reverse(123));

        Console.WriteLine(reverse(456));

        Console.WriteLine(reverse(731));

    }

    public static int reverse(int number, int result = 0, int reminder = 0)

    {

        if (number == 0)

        {

            return result * 10 + reminder;

        }

        return reverse(number / 10, result * 10 + reminder, number % 10);

    }

}