Magic Letter

            char c1 = char.Parse(Console.ReadLine());
            char c2 = char.Parse(Console.ReadLine());
            char c3 = char.Parse(Console.ReadLine());

            for (int i = c1; i <= c2; i++)
            {
                for (int j = c1; j <= c2; j++)
                {
                    for (int k = c1; k <= c2; k++)
                    {
                        if (i != c3 && j != c3 && k != c3)
                        {
                            Console.Write($"{(char)i}{(char)j}{(char)k} ");
                        }
                    }
                }
            }
            Console.WriteLine();