                           3
                       _.-' `---....____
                      2                 6
                  _.-' \        ___..--' `--..___
                 1      [3]    4                 8
                / \          _' `._          _.-' `._
               []  [2]      [3]    5        7        9
                                 _' \     _' \     _' \
                                [4]  [6] [6]  [8] [8]  []
 
