Prog. Fundamentals Exam Prep III - 03. Rage Quit

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

namespace _14_ExamPreparation3
{
    class Program
    {
      static void Main(string[] args)
        {
            string input = Console.ReadLine();
            string pattern = @"([^\d]+)(\d+)";
            StringBuilder sb = new StringBuilder();
            MatchCollection matches = Regex.Matches(input, pattern);

            foreach (Match match in matches)
            {
                string str = match.Groups[1].ToString().ToUpper();
                int charCount = int.Parse(match.Groups[2].ToString());
                for (int i = 0; i < charCount; i++)
                {
                    sb.Append(str);
                }
            }
            var count = sb.ToString().Distinct().Count();
            Console.WriteLine($"Unique symbols used: {count}");
            Console.WriteLine(sb);

        }
    }
}