bbb bbc bbo bbr bcb bcc bco bcr bcz bob boc boo bor boz brb bro brr brz bzo bzr bzz c-- cbb cbc cbo cbr cbz ccb ccc cco ccr ccz co- cob coc coo cor coz crb crc cro crr crz cz- czc czo ob- obb obc obo obr oc- ocb occ oco ocr ocz oo- oob ooc ooo oor or- orb orc oro orr orz ozo ozz rbb rbc rbo rbr rcb rcc rco rcr rob roc roo ror roz rrb rrc rrr rzb rzo zbb zbc zbr zco zo- zob zoc zoo zor zro zzr zzz