class DLinkedList:
    def __init__(self) -> None:
        self._len = 0
        self._head = _Node()
        self._head.next = self._head
        self._head.prev = self._head
        self._curr: Tuple[_Node, int] = (self._head, 1)

    def at_head(self) -> bool:
        if self._curr[0] is self._head:
            return True
        else:
            return False

    def get_curr(self) -> Tuple[Any, int]:
        return (self._curr[0].data, self._curr[1])
        
    def set_curr(self, data: Any) -> None:
        if self.at_head():
            raise IndexError("Empty or curr is at head (try next or prev?)")
        else:
            self._curr[0].data = data


    def next(self, n: int = 1) -> Tuple[Any, int]:
        """Move the current position one forward"""
        temp_node, temp_index = self._curr[0], self._curr[1]
        for i in range(n):
            temp_node = temp_node.next
            temp_index = -1 if temp_node is self._head else temp_index + 1
        self._curr = (temp_node, self._len if temp_node is self._head else temp_index)
        return self.get_curr()
    
    def prev(self, n: int = 1) -> Tuple[Any, int]:
        """Move the current position one forward"""
        temp_node, temp_index = self._curr[0], self._curr[1]
        for _ in range(n):
            temp_node = temp_node.prev
            temp_index = self._len if temp_node is self._head else temp_index - 1
        self._curr = (temp_node, temp_index)
        return self.get_curr()
    
    def __len__(self) -> int:
        return self._len

    def __getitem__(self, index: int) -> Any:
        tmp = self._head.next
        for _ in range(index):
            if tmp is self._head:
                break
            else:
                tmp = tmp.next
        return tmp.data

    

class _Node:
    def __init__(self,
                 data: Any = None,
                 prev: Union[_Node, None] = None,
                 next: Union[_Node, None] = None) -> None:
        self.data = data
        self.prev = prev
        self.next = next