Rage Quit - String and Text Proccessing

using System;
using System.Linq;
using System.Text;

namespace _10RageQuit
{
    class Program
    {
        static void Main(string[] args)
        {
            char[] input = Console.ReadLine().ToUpper().ToCharArray();
            string toBeRepeated = "";
            string repetition = "";
            StringBuilder result = new StringBuilder();

            for (int i = 0; i < input.Length; i++)
            {
                if (char.IsDigit(input[i]))
                {
                    repetition += input[i].ToString();

                    if (i + 1 < input.Length && char.IsDigit(input[i + 1]))
                    {
                        repetition += input[i + 1].ToString();
                    }

                    int counter = int.Parse(repetition);

                    if (counter == 0) // Don't need to add that to the result.
                    {
                        toBeRepeated = "";
                        repetition = "";
                    }
                    else
                    {
                        for (int j = 0; j < counter; j++)
                        {
                            result.Append(toBeRepeated);

                            if (j == counter - 1) // If we are at the last iteration we clear the strings.
                            {
                                toBeRepeated = "";
                                repetition = "";
                            }
                        }
                    }
                }
                else
                {
                    toBeRepeated += input[i];
                }
            }

            int uniqueSymbols = result.ToString().Distinct().Count();
            string resultString = result.ToString();

            Console.WriteLine($"Unique symbols used: {uniqueSymbols}");
            Console.WriteLine(resultString);
        }
    }
}