public static void Main(String[] args)
        {
            Stack s = new Stack();

            s.Push(1);
            Console.WriteLine("Size of Stack: " + s.Size() + "\tTop : " + s.Top());
            s.Push(7);
            Console.WriteLine("Size of Stack: " + s.Size() + "\tTop : " + s.Top());
            s.Push(9);
            Console.WriteLine("Size of Stack: " + s.Size() + "\tTop : " + s.Top());

            s.Pop();
            Console.WriteLine("Size of Stack: " + s.Size() + "\tTop : " + s.Top());
            s.Pop();
            Console.WriteLine("Size of Stack: " + s.Size() + "\tTop : " + s.Top());

            s.Push(5);
            Console.WriteLine("Size of Stack: " + s.Size() + "\tTop : " + s.Top());

            /*
             * Output :
             *
             * current size: 4
             * 4
             * 3
             * 2
             * current size: 2
             */
        }