def remove_dups_wothout_set(head):
    """
    Time Complexity: O(N^2)
    Space Complexity: O(1)
    """
    current = head
    while current:
        runner = current
        while runner.next:
            if runner.next.val == current.val:
                runner.next = runner.next.next
            else:
                runner = runner.next
        current = current.next
