class Node:
    def __init__(self, val):
        self.val = val
        self.both = 0

    def __str__(self):
        return str(self.val)

class XORLinkedList:
    def __init__(self):
        self.head = Node(None)
        self.tail = Node(None)

    def add(element):
        newNode = Node(element)
        if self.head.val == None:
            self.head = self.tail = newNode
        else:
            newNode.both = get_pointer(self.tail)
            self.tail.both = self.tail.both ^ get_pointer(newNode)
            self.tail = newNode

    def get(ind):
        previousAddr = 0
        current = this.head
        for i in range(0,ind-1):
            temp = get_pointer(current)
            current = dereference_pointer(previousAddr^current.both)
            previousAddr = temp
            if curret.both == previousAddr and i < ind-2:
                print("Invalid index.")
                return None
        return current