[C# Basics]Problem6.FourDigitNumber

using System;
/* Write a program that takes as input a four-digit number in format abcd (e.g. 2011) and performs the following:
 *  Calculates the sum of the digits (in our example 2+0+1+1 = 4).
 *  Prints on the console the number in reversed order: dcba (in our example 1102).
 *  Puts the last digit in the first position: dabc (in our example 1201).
 *  Exchanges the second and the third digits: acbd (in our example 2101).
 *  The number has always exactly 4 digits and cannot start with 0.
 *  Examples:
 *  n       sum of digits   reversed    last digit in front     second and third digits exchanged
 *  2011    4               1102        1201                    2101
 *  3333    12              3333        3333                    3333
 *  9876    30              6789        6987                    9786 */
class FourDigitNumber
{
    static void Main()
    {
        int number = 0;
        Console.Write("Enter a integer between 1000 and 9999: ");

        if (int.TryParse(Console.ReadLine(), out number) && number >= 1000 && number <= 9999) //prevent to work whit an invalid data as "1d12" or 0-starting strings.
        {
            Console.Clear();
            //extracting the digits
            int firstDigit = number/1000;
            int secondDigit = ((number / 100) % 10);
            int thirdDigit = ((number / 10) % 10);
            int fourDigit = number % 10;

            //making varibles to pattern that will be printed
            int digitsSum = firstDigit + secondDigit + thirdDigit + fourDigit;
            string reversed = fourDigit.ToString() + thirdDigit.ToString() + secondDigit.ToString() + firstDigit.ToString();
            string lastInFront = fourDigit.ToString() + firstDigit.ToString() + secondDigit.ToString() + thirdDigit.ToString();
            string exchangedDigids = firstDigit.ToString() + thirdDigit.ToString() + secondDigit.ToString() + fourDigit.ToString();

            Console.WriteLine("n\tsum\treversed\tlast in front\texchanged digits"); //prints header
            Console.WriteLine("{0}\t{1}\t{2}\t\t{3}\t\t{4}", number, digitsSum, reversed, lastInFront, exchangedDigids);
        }
        else
        {
            Console.WriteLine("You have entered invalid data!");
        }
    }
}