0: Test for source tree numbering 1: Level A 2: Level B 3: Level B 4: Level C 5: Level B 6: Level C 7: Level D 8: Level A 9: Level B 10: Level C 11: Level D 12: Level E 13: Level A 14: Level B 15: Level C 16: Level D 17: Level E 18: Level D 19: Level E 20: Level C 21: Level D 22: Level B