4

                                 +5

9

                                     0

                                   +1

1

                                 2

                               +3

5

                                         6

                                      + 7

13

                                        7

                                      +8

15

                                  9

                              +10

19

                                       5

                                     +6

11

                                       3

                                     +4

7

                                        1

                                      +2

3

                                  9

                                +8

17

                                   7

                                 +6

13

                                       8

                                     +7

15