-er a-a a-b aaa aab aae aak aao aap aar aas ab- aba abb abe abk abo abp abr abs aea aeb aee aek aeo aep aer aes aka akb ake akk ako akp akr aks aoa aob aoe aok aoo aop aor aos ap- apa apb ape apk apo app apr aps ar- ara arb are ark aro arp arr ars as- asa asb ase ask aso asp asr ass b-p baa bab bae bak bao bap bar bas bba bbb bbe bbk bbo bbp bbr bbs be- bea beb bee bek beo bep ber bes bka bkb bke bkk bko bkp bkr bks boa bob boe bok boo bop bor bos bpa bpb bpe bpo bpp bpr bps bra brb bre brk bro brp brr brs bsa bsb bse bsk bso bsp bsr bss eaa eab eae eak eao eap ear eas eba ebb ebe ebk ebo ebp ebr ebs eea eeb eee eek eeo eep eer ees eka ekb eke eko ekp ekr eks eo- eoa eob eoe eok eoo eop eor eos ep- epa epb epe epo epp epr eps era erb ere erk ero erp err ers es- esa esb ese esk eso esp esr ess ka- kaa kab kae kak kao kap kar kas kba kbb kbe kbk kbo kbp kbr kbs ke- kea keb kee kek keo kep ker kes kkb kke kkk kkp kkr kks koa kob koe kok koo kop kor kos kpa kpe kpk kpo kpp kpr kps kra krk kro krp krr krs ksa ksb kse ksk kso ksp ksr kss oaa oab oae oak oao oap oar oas ob- oba obb obe obk obo obp obr obs oea oeb oee oeo oep oer oes oka okb oke okk oko okp okr oks oo- ooa oob ook ooo oop oor oos op- opa opb ope opk opo opp opr ops or- ora orb ore ork oro orp orr ors os- osa osb ose osk oso osp osr oss p-p paa pab pae pak pao pap par pas pba pbb pbe pbk pbo pbp pbr pbs pea peb pee pek peo pep per pes pka pkb pke pko pkp pkr pks poa pob poe pok poo pop por pos ppa ppb ppe ppk ppo ppp ppr pps pra prb pre prk pro prp prr prs ps- psa psb pse psk pso psp psr pss ra- raa rab rae rak rao rap rar ras rba rbb rbe rbk rbo rbp rbr rbs re- rea reb ree rek reo rep rer res rkb rke rkk rko rkp rks roa rob roe rok roo rop ror ros rpa rpb rpe rpk rpo rpp rpr rps rra rrb rrk rrp rrr rrs rsa rsb rse rsk rso rsp rsr rss saa sab sae sak sao sap sar sas sba sbb sbe sbk sbo sbp sbr sbs se- sea seb see sek seo sep ser ses sk- ska skb ske skk sko skp skr sks soa sob soe sok soo sop sor sos spa spb spe spk spo spp spr sps sr- sra srb sre srk sro srp srr srs ss- ssa ssb sse ssk sso ssp ssr sss