b-p bbb bbo bbp bbr bbs bbt bob boo bop bor bos bot bpb bpo bpp bpr bps bpt brb bro brp brr brs brt bsb bso bsp bsr bss bst btb bto btp btr bts btt ob- obb obo obp obr obs obt oo- oob ooo oop oor oos oot op- opb opo opp opr ops opt or- orb oro orp orr ors ort os- osb oso osp osr oss ost ot- otb oto otp otr ots ott p-p pbb pbo pbp pbr pbs pbt pob poo pop por pos pot ppb ppo ppp ppr pps ppt prb pro prp prr prs prt ps- psb pso psp psr pss pst pt- ptb pto ptp ptr pts ptt rbb rbo rbp rbr rbs rbt rob roo rop ror ros rot rpb rpo rpp rpr rps rpt rrb rrp rrr rrs rrt rsb rso rsp rsr rss rst rtb rto rtp rtr rts rtt sbb sbo sbp sbr sbs sbt sob soo sop sor sos sot spb spo spp spr sps spt sr- srb sro srp srr srs srt ss- ssb sso ssp ssr sss sst stb sto stp str sts stt tbb tbo tbp tbr tbs tbt to- tob too top tor tos tot tpb tpo tpp tpr tps tpt trb tro trp trr trs trt tsb tso tsp tsr tss tst ttb tto ttp ttr tts ttt