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