level1 a
 child1 a
 level2 a
  child2 a
  level3 a
   child3 a
level1 b
 child1 b
 level2 b
  child2 b
level1 c
 child1 c
 level2 c
  child2 c
  level3 c
   child3 c
 level2 d
  child2 d
level1 e
 child1 e
 level2 e
  child2 e
 level2 f
  child2 f
level1 g
 child1 g
level1 h
 child1 h