-er b-p bbb bbe bbi bbk bbo bbp bbr bbs be- beb bee bei bek beo bep ber bes bi- bib bie bii bik bio bip bir bis bkb bke bkk bko bkp bkr bks bob boe boi bok boo bop bor bos bpb bpe bpi bpo bpp bpr bps brb bre bri brk bro brp brr brs bsb bse bsi bsk bso bsp bsr bss ebb ebe ebi ebk ebo ebp ebr ebs eeb eee eek eeo eep eer ees eib eie eii eik eio eip eir eis ekb eke eki eko ekp ekr eks eo- eob eoe eoi eok eoo eop eor eos ep- epb epe epi epo epp epr eps erb ere eri erk ero erp err ers es- esb ese esi esk eso esp esr ess ibb ibe ibi ibk ibo ibp ibr ibs ie- iee iei iek iep ier ies iib iie iii iio iip iir iis ikb ike iki ikk iko ikr iks io- iob ioe ioi ioo iop ior ios ipb ipe ipi ipo ipp ipr ips ir- irb ire iri irk iro irp irr irs is- isb ise isi isk iso isp isr iss kbb kbe kbi kbk kbo kbp kbr kbs ke- keb kee kei kek keo kep ker kes kib kie kii kik kio kip kir kis kkb kke kki kkk kkp kkr kks kob koe koi kok koo kop kor kos kpe kpi kpk kpo kpp kpr kps kri krk kro krp krr krs ksb kse ksi ksk kso ksp ksr kss o-i ob- obb obe obi obk obo obp obr obs oeb oee oei oeo oep oer oes oib oie oii oik oio oip oir ois okb oke oki okk oko okp okr oks oo- oob ooi ook ooo oop oor oos op- opb ope opi opk opo opp opr ops or- orb ore ori ork oro orp orr ors os- osb ose osi osk oso osp osr oss p-p pbb pbe pbi pbk pbo pbp pbr pbs peb pee pei pek peo pep per pes pib pie pii pik pio pip pir pis pkb pke pki pko pkp pkr pks pob poe poi pok poo pop por pos ppb ppe ppi ppk ppo ppp ppr pps prb pre pri prk pro prp prr prs ps- psb pse psi psk pso psp psr pss rbb rbe rbi rbk rbo rbp rbr rbs re- reb ree rei rek reo rep rer res rib rie rii rik rio rip rir ris rkb rke rkk rko rkp rks rob roe roi rok roo rop ror ros rpb rpe rpi rpk rpo rpp rpr rps rrb rri rrk rrp rrr rrs rsb rse rsi rsk rso rsp rsr rss sbb sbe sbi sbk sbo sbp sbr sbs se- seb see sei sek seo sep ser ses sib sie sii sik sio sip sir sis sk- skb ske ski skk sko skp skr sks sob soe soi sok soo sop sor sos spb spe spi spk spo spp spr sps sr- srb sre sri srk sro srp srr srs ss- ssb sse ssi ssk sso ssp ssr sss