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

            s.push(1);
            s.push(2);
            s.push(3);
            Console.WriteLine("current size: " + s.size());
            Console.WriteLine(s.top());
            s.pop();
            Console.WriteLine(s.top());
            s.pop();
            Console.WriteLine(s.top());
            Console.WriteLine("current size: " + s.size());

            /*
             * Output :
             * current size: 3
             * 3
             * 2
             * 1
             * current size: 1
             */
        }