-er b-p bbb bbe bbf bbk bbo bbp bbr bbs be- beb bee bef bek beo bep ber bes bfb bfe bff bfo bfp bfr bfs bkb bke bkf bkk bko bkp bkr bks bob boe bof bok boo bop bor bos bpb bpe bpf bpo bpp bpr bps brb bre brf brk bro brp brr brs bsb bse bsf bsk bso bsp bsr bss ebb ebe ebf ebk ebo ebp ebr ebs eeb eee eef eek eeo eep eer ees ef- efb efe eff efo efp efr efs ekb eke ekf eko ekp ekr eks eo- eob eoe eof eok eoo eop eor eos ep- epb epe epf epo epp epr eps erb ere erf erk ero erp err ers es- esb ese esf esk eso esp esr ess fbb fbe fbf fbk fbo fbp fbr fbs feb fee fef fek feo fep fer fes ffe fff ffk ffo ffp ffr ffs fkb fkf fkk fkp fob foe fof fok foo fop for fos fpb fpe fpk fpo fpp fpr fps frb fre frf frk fro frp frr frs fsb fse fsf fsk fso fsp fsr fss kbb kbe kbf kbk kbo kbp kbr kbs ke- keb kee kef kek keo kep ker kes kff kfo kfs kkb kke kkk kkp kkr kks kob koe kof kok koo kop kor kos kpe kpf kpk kpo kpp kpr kps krf krk kro krp krr krs ksb kse ksf ksk kso ksp ksr kss ob- obb obe obf obk obo obp obr obs oeb oee oef oeo oep oer oes of- ofb ofe off ofo ofp ofr ofs okb oke okk oko okp okr oks oo- oob oof ook ooo oop oor oos op- opb ope opf opk opo opp opr ops or- orb ore orf ork oro orp orr ors os- osb ose osf osk oso osp osr oss p-p pbb pbe pbf pbk pbo pbp pbr pbs peb pee pef pek peo pep per pes pfb pfe pff pfk pfo pfp pfr pfs pkb pke pkf pko pkp pkr pks pob poe pof pok poo pop por pos ppb ppe ppf ppk ppo ppp ppr pps prb pre prf prk pro prp prr prs ps- psb pse psf psk pso psp psr pss rbb rbe rbf rbk rbo rbp rbr rbs re- reb ree ref rek reo rep rer res rfb rfe rff rfk rfo rfp rfr rfs rkb rke rkf rkk rko rkp rks rob roe rof rok roo rop ror ros rpb rpe rpf rpk rpo rpp rpr rps rrb rrf rrk rrp rrr rrs rsb rse rsf rsk rso rsp rsr rss sbb sbe sbf sbk sbo sbp sbr sbs se- seb see sef sek seo sep ser ses sfb sfe sff sfk sfo sfp sfr sfs sk- skb ske skf skk sko skp skr sks sob soe sof sok soo sop sor sos spb spe spf spk spo spp spr sps sr- srb sre srf srk sro srp srr srs ss- ssb sse ssf ssk sso ssp ssr sss