3. Memory game

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Threading.Channels;

namespace _3._Memory_game
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> sequence = Console.ReadLine().Split().ToList();

            int moves = 0;
            while (true)

            {
                string command = Console.ReadLine();
                if (command == "end")
                {
                    break;
                }
                moves++;
                int[] indexes = command.Split().Select(int.Parse).ToArray();
                int firstIndex = indexes[0];
                int secondIndex = indexes[1];
                if (indexes[0] < indexes[1])
                {
                    firstIndex = indexes[1];
                    secondIndex = indexes[0];
                }

                if (firstIndex == secondIndex || firstIndex < 0 || secondIndex < 0 || secondIndex >= sequence.Count ||
                    firstIndex >= sequence.Count)
                {
                    Console.WriteLine("Invalid input! Adding additional elements to the board");
                    //add additional elements
                    int middle = sequence.Count / 2;
                    sequence.Insert(middle, $"-{moves}a");
                    sequence.Insert(middle + 1, $"-{moves}a");
                }
                else
                {

                    if (sequence[firstIndex] == sequence[secondIndex])
                    {
                        Console.WriteLine($"Congrats! You have found matching elements - {sequence[firstIndex]}!");

                        sequence.RemoveAt(firstIndex);
                        sequence.RemoveAt(secondIndex);

                    }
                    else
                    {
                        Console.WriteLine("Try again!");
                        continue;
                    }
                    if (sequence.Count == 0)
                    {
                        Console.WriteLine($"You have won in {moves} turns!");
                        return;
                    }

                }
            }



            if (sequence.Count > 0)
            {
                Console.WriteLine("Sorry you lose :(");
                Console.WriteLine(string.Join(" ", sequence));
            }


        }
    }
}