public static void driver()
        {
            SetOfStacks3_3 stk = new SetOfStacks3_3();
            for (int i = 0; i < 15; i++)
            {
                stk.push(i);
            }

            while (!stk.IsEmpty())
                Console.WriteLine("Popped = {0}", stk.pop());
        }
        public static void driver()
        {
            SetOfStacks3_3 stk = new SetOfStacks3_3();

            for (int i = 0; i < 15; i++)
            {
                stk.push(i);
            }

            while (!stk.IsEmpty())
            {
                Console.WriteLine("Popped = {0}", stk.pop());
            }
        }