RageQuit(NoRegex)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace _09._Rage_Quit
{
    class Program
    {
        static void Main(string[] args)
        {
            string rageBuilder = Console.ReadLine();
            StringBuilder rageMassage = new StringBuilder();

            int lastDigitIndex = 0;
            int digitIndex = 0;
            for (int i = 0; i < rageBuilder.Length; i++)
            {
                char currentSymbol = rageBuilder[i];
                int timesToPrint = 0;

                if (int.TryParse(currentSymbol.ToString(), out int firstDigit))
                {
                    timesToPrint = firstDigit;
                    digitIndex = i;
                    bool numberHasTwoDigits = false;
                    if (i < rageBuilder.Length-1)
                    {
                        char nextSymbol = rageBuilder[i + 1];

                        if (int.TryParse(nextSymbol.ToString(), out int nextDigit ))
                        {
                            timesToPrint = firstDigit * 10 + nextDigit;
                            numberHasTwoDigits = true;
                        }

                    }


                    string massageToPrint = rageBuilder.Substring(lastDigitIndex, digitIndex-lastDigitIndex);
                    lastDigitIndex = digitIndex + 1;
                    i = lastDigitIndex ;
                    if (numberHasTwoDigits)
                    {
                        lastDigitIndex++;
                    }

                    StringBuilder currentMassage = new StringBuilder();
                    for (int k = 0; k < massageToPrint.Length; k++)
                    {
                        char currentChar = massageToPrint[k];
                        if (char.IsLetter(currentChar))
                        {
                            currentChar = char.ToUpper(currentChar);
                        }

                        currentMassage.Append(currentChar);

                    }

                    for (int l = 0; l < timesToPrint; l++)
                    {
                        rageMassage.Append(currentMassage);
                    }

                }

            }

            var count = rageMassage.ToString().Distinct().Count();
            Console.WriteLine($"Unique symbols used: {count}");
            //Console.WriteLine(string.Join(" ", uniqeSymbols));
            Console.WriteLine(rageMassage);


        }
    }
}