RageQuit - No RegEx

RageQuit.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

class RageQuit
{
    static void Main()
    {
        string input = Console.ReadLine();

        StringBuilder word = new StringBuilder();
        StringBuilder count = new StringBuilder();
        StringBuilder result = new StringBuilder();
        var inDigits = false;
        for (int i = 0; i < input.Length; i++)
        {
            char ch = Char.ToUpper(input[i]);
            if (inDigits)
            {
                // Scan for digits
                if (Char.IsDigit(ch))
                {
                    count.Append(ch);
                }
                else
                {
                    // word + count found
                    for (int c = 0; c < int.Parse(count.ToString()); c++)
                        result.Append(word);
                    inDigits = false;
                    word.Clear();
                    word.Append(ch);
                }
            }
            else
            {
                // Scan for letters
                if (!Char.IsDigit(ch))
                {
                    word.Append(ch);
                }
                else
                {
                    // digit found
                    inDigits = true;
                    count.Clear();
                    count.Append(ch);
                }
            }
        }

        for (int c = 0; c < int.Parse(count.ToString()); c++)
            result.Append(word);


        Dictionary<char, bool> charOccurs = new Dictionary<char, bool>();
        foreach (var ch in result.ToString())
        {
            charOccurs[ch] = true;
        }
        var uniqueChars = charOccurs.Keys.Count;

        Console.WriteLine($"Unique symbols used: {uniqueChars}");
        Console.WriteLine(result.ToString());
    }
}