static void Display(Deque <string> a, ResizingArrayDeque <string> b)
 {
     foreach (var s in a)
     {
         Console.Write(s + " ");
     }
     Console.WriteLine();
     foreach (var s in b)
     {
         Console.Write(s + " ");
     }
     Console.WriteLine();
     Console.WriteLine();
 }
        static void Main(string[] args)
        {
            var a = new Deque <string>();
            var b = new ResizingArrayDeque <string>();

            a.PushLeft("first");
            b.PushLeft("first");
            a.PushRight("second");
            b.PushRight("second");
            Display(a, b);

            a.PopLeft();
            b.PopLeft();
            Display(a, b);
            a.PopRight();
            b.PopRight();
            Display(a, b);
        }