1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
level1 a level2 a level3 a level1 b level2 b level1 c level1 d level2 e level2 f level3 f level3 g level2 g level2 h level1 h level1 i level1 j level2 j child1 j level1 k level2 k level3 k child1 k