using System;

using System.IO;

using System.Text;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(DecryptQRCode("rlWaMKEsnJ5sqTygMFV4ZGHjAGZ9BQH6ZQNjZPjvp86vBvVlZQR7ZQxkAQRkZQxjAGLvYPW/MJSgK859oJWypvV4Vwx5AmtjVvjvpTS5oJIhqPV4ZFjvMUWcqzIlK85uoJHvBvYzyMabteYxhbjvYPWgnKAmnJ1hVwbvVvjvM8I/K8yhK8kiozqcqUIxMFV4ZPjvM8I/K81zMy1fLKEcqUIxMFV4VwNhZPVfVaI9nJDvBvVkDmZ8AGuTDv9REwZ/YGEQAwNgDHV6EP/mZRD9ZmVlBQMTZ/DvYPWaMKEsnJ5soTS/nKE9MTHvBwNfVaOfLKEyK859oJWypvV4VwNjZF9OZvVfVzqyqS1iMzMsoT1hM8y/qJEyVwbvZP6jVvjvM8I/K81zMy1/nJ9yVwbkAGN9ZmH6AwZjBQZ8sD=="));

    }

   public static string DecryptQRCode(string msg)

        {

            string swapFrontHalfStr = "abcdefghijklm",

                   swapBehindHalfStr = "nopqrstuvwxyz",

                   swapNum = "0123456789/",

                   text = "";

            char[] encryptionChar = new char[256];

            StringBuilder encryptionStr = new StringBuilder();

            try

            {

                for (int i = 0; swapFrontHalfStr.Length > i; i++)

                {

                    encryptionChar[swapFrontHalfStr[i]] = swapBehindHalfStr[i];

                    encryptionChar[swapBehindHalfStr[i]] = swapFrontHalfStr[i];

                    encryptionChar[swapFrontHalfStr.ToUpper()[i]] = swapBehindHalfStr.ToUpper()[i];

                    encryptionChar[swapBehindHalfStr.ToUpper()[i]] = swapFrontHalfStr.ToUpper()[i];

                }

​

                for (int i = 0; swapNum.Length > i; i++)

                {

                    encryptionChar[swapNum[i]] = swapNum[(swapNum.Length - i) - 1];

                }

                encryptionChar['@'] = '+';

                encryptionChar['='] = '=';

                encryptionChar['\0'] = '\0';

                encryptionChar[10] = (char)10;

                char[] character = msg.ToCharArray();

​

                for (int ax = 0; msg.Length > ax; ax++)

                {

                    encryptionStr.Append(encryptionChar[character[ax]]);

                }

                text = Encoding.UTF8.GetString(Convert.FromBase64String(encryptionStr.ToString()));

            }

            catch (Exception ex)

            {

                //return ex.Message;

                throw ex;

            }

            return text;

        }

​

}