03. Treasure Finder

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

namespace TreasureFinder
{
    class Program
    {
        static string SubStringFinder(string str, char start, char end)
        {
            int startIndex = str.IndexOf(start) + 1;
            int endIndex = str.LastIndexOf(end) - startIndex;

            return str.Substring(startIndex, endIndex);
        }
        static void Main()
        {
            var key = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);

            string command;

            while ((command = Console.ReadLine()) != "find")
            {
                char[] message = command.ToCharArray();

                for (int i = 0; i < command.Count(); i++)
                {
                    message[i] = (char)(message[i] - key[i % key.Length]);
                }

                string str = new string(message);
                string type = SubStringFinder(str, '&', '&');
                string coordinates = SubStringFinder(str, '<', '>');

                Console.WriteLine($"Found {type} at {coordinates}");
            }
        }
    }
}