b-p bbb bbc bbo bbp bbr bcb bcc bco bcp bcr bob boc boo bop bor bpb bpc bpo bpp bpr brb bro brp brr c-- cbb cbc cbo cbp cbr ccb ccc cco ccp ccr co- cob coc coo cop cor cpb cpc cpo cpp cpr crb crc cro crp crr ob- obb obc obo obp obr oc- ocb occ oco ocp ocr oo- oob ooc ooo oop oor op- opb opc opo opp opr or- orb orc oro orp orr p-p pbb pbc pbo pbp pbr pcb pcc pco pcp pcr pob poc poo pop por ppb ppc ppo ppp ppr prb prc pro prp prr rbb rbc rbo rbp rbr rcb rcc rco rcp rcr rob roc roo rop ror rpb rpc rpo rpp rpr rrb rrc rrp rrr