Santa'sSecretHelper

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

namespace SantasSecretHelper
{
    class Program
    {
        static void Main(string[] args)
        {
            int key = int.Parse(Console.ReadLine());
            string message = string.Empty;
            var dictNameAndBehaviour = new Dictionary<string, string>();

            while((message=Console.ReadLine())!="end")
            {
                string decryptMessage = string.Empty;
                for (int i = 0; i < message.Length; i++)
                {
                    int decryptValue =  message[i] - key;
                    decryptMessage += (char)decryptValue;
                }

                Regex regexForNameAndBehaviour = new Regex(@"@(?<name>[A-Za-z]+(?![@\-!:>]))[^@\-!:>]*!(?<behaviour>G|N)!");
                MatchCollection matchNameAndBehaviour = regexForNameAndBehaviour.Matches(decryptMessage);
                if (regexForNameAndBehaviour.IsMatch(decryptMessage))
                {
                    string name = matchNameAndBehaviour[0].Groups["name"].Value;
                    string behaviour = matchNameAndBehaviour[0].Groups["behaviour"].Value;
                    dictNameAndBehaviour[name] = behaviour;
                }
            }

            var dictonaryWihtGoodChildren = dictNameAndBehaviour.Where(x => x.Value == "G");

            foreach (var kvp in dictonaryWihtGoodChildren )
            {
                string name = kvp.Key;
                Console.WriteLine(name);
            }
        }
    }
}