code: def remove_dups_wothout_set(head):
      
      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
docs: Time Complexity: O(N^2)
      Space Complexity: O(1)