05. Key Replacer

using System;
using System.Text.RegularExpressions;
using System.Linq;
using System.Globalization;
using System.Numerics;

class Program
{
    static void Main(string[] args)
    {
        string key = Console.ReadLine();
        string patternKey = @"(?<start>[a-zA-Z]+)(\||\\|<)((\w*\W*)*(\||\\|<))*(?<end>[a-zA-Z]+)";
        string text = Console.ReadLine();
        Match matchKey = Regex.Match(key, patternKey);
        string start ="{" + matchKey.Groups["start"].Value + "}";
        string end = "{" + matchKey.Groups["end"].Value + "}";
        string patternText = $@"{start}(?<between>.*?){end}";
        MatchCollection matches = Regex.Matches(text, patternText);
        string final = null;
        foreach (Match item in matches)
        {
            final+=item.Groups["between"].Value;
        }

        Console.WriteLine(final);

    }
}