Kwadrat z pustym środkiem C#

            int i, j, k, l,n;
            Console.WriteLine("Podaj bok kwadratu: ");
            int a = int.Parse(Console.ReadLine());
            for (i = 1; i <= a; i++)
            {
                if (i == 1)
                {
                    for (j = 1; j <= a; j++)
                    {
                        Console.Write("@");
                    }
                    Console.Write("\n");
                }
                else
                {
                    if (i == a)
                    {
                        for (k = 1; k < a ; k++)
                        {
                            Console.Write("@");
                        }
                    }
                    else
                    {
                        for (l = 1; l <= 1; l++)
                        {
                            Console.Write("@");
                        }
                        for (n = 1; n <= a - 2; n++)
                        {
                            Console.Write(" ");
                        }
                    }
                    Console.WriteLine("@");
                }
            }

            Console.WriteLine("");