0: Test for source tree numbering 1: Level A 2: Level B 3: Level B 0: Level C 1: Level B 0: Level C 1: Level D 2: Level A 3: Level B 0: Level C 1: Level D 2: Level E 3: Level A 4: Level B 0: Level C 1: Level D 2: Level E 3: Level D 4: Level E 0: Level C 1: Level D 2: Level B