static void Main()
        {
            Console.WriteLine("Input a number");
            int number = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine("Input a second number (optional)");
            string         input = Console.ReadLine();
            MathOperations math  = new MathOperations();

            if (input != "")
            {
                int number2 = Convert.ToInt32(input);
                Console.WriteLine(math.Add(number, number2));
            }
            else
            {
                Console.WriteLine(math.Add(number));
            }
            Console.Read();
        }