NIL
1.2.3.4.5.6.7.8.9.10.11
12.13.14.15.16.17
12.13
12.13.14.15.16.17.18.19
20.21.22.23.24.25.26.27
28
1.2.3.4.5.6.7.8.9
20.21.22.23