-ic bbb bbc bbi bbk bbo bbr bbs bcb bcc bci bck bco bcr bcs bi- bib bic bii bik bio bir bis bkb bkc bkk bko bkr bks bob boc boi bok boo bor bos brb bri brk bro brr brs bsb bsc bsi bsk bso bsr bss c-- cbb cbc cbi cbk cbo cbr cbs ccb ccc cci cck cco ccr ccs ci- cib cic cii cik cio cir cis ckb ckc cki cko cks co- cob coc coi cok coo cor cos crb crc cri crk cro crr crs csb csc csi csk cso csr css ibb ibc ibi ibk ibo ibr ibs icb icc ici ick ico icr ics iib iic iii iio iir iis ikb ikc iki ikk iko ikr iks io- iob ioc ioi ioo ior ios ir- irb irc iri irk iro irr irs is- isb isc isi isk iso isr iss kbb kbc kbi kbk kbo kbr kbs kcb kcc kci kck kcr kcs kib kic kii kik kio kir kis kkb kkc kki kkk kkr kks kob koc koi kok koo kor kos krc kri krk kro krr krs ksb ksc ksi ksk kso ksr kss o-i ob- obb obc obi obk obo obr obs oc- ocb occ oci ock oco ocr ocs oib oic oii oik oio oir ois okb okc oki okk oko okr oks oo- oob ooc ooi ook ooo oor oos or- orb orc ori ork oro orr ors os- osb osc osi osk oso osr oss rbb rbc rbi rbk rbo rbr rbs rcb rcc rci rco rcr rcs rib ric rii rik rio rir ris rkb rkc rkk rko rks rob roc roi rok roo ror ros rrb rrc rri rrk rrr rrs rsb rsc rsi rsk rso rsr rss sbb sbc sbi sbk sbo sbr sbs scb scc sci sck sco scr scs sib sic sii sik sio sir sis sk- skb skc ski skk sko skr sks sob soc soi sok soo sor sos sr- srb src sri srk sro srr srs ss- ssb ssc ssi ssk sso ssr sss