| | |--> 2. c
  | | |--> 2. d
  | | |--> 2. e
  | | |--> 3. d
  | | `--> 3. e
  | | | +--> 1.D
  | | | +--> 3.AB
  | | | +--> 3.E
  | | | +--> 4.C
  | | +--> 2.c
  | | `--> 2.d