static void Main(string[] args)
{
DoublyLinkedList list = new DoublyLinkedList();
list.AddFirst("1");
list.AddFirst("2");
list.AddFirst("3");
list.AddLast("4");
list.AddLast("5");
list.AddFirst("6");
list.DisplayList(); // 6 3 2 1 4 5
Console.WriteLine();
Console.WriteLine(list.GetAndRemoveFirst());
list.DisplayList(); // 3 2 1 4 5
Console.WriteLine();
Console.WriteLine(list.GetAndRemoveLast());
list.DisplayList(); // 3 2 1 4
var findEl = list[2];
Console.WriteLine();
list.InsertAfter(findEl, "7");
list.DisplayList(); // 3 2 1 7 4
findEl = list[1];
Console.WriteLine();
list.RemoveElement(findEl);
list.DisplayList(); // 3 1 7 4
Console.WriteLine();
list.AddFirst("8");
list.AddLast("9");
Console.ReadLine();
}