-er a-a a-b aaa aab aae aak aam aao aar aas ab- aba abb abe abk abm abo abr abs aea aeb aee aek aem aeo aer aes aka akb ake akk akm ako akr aks ama amb ame amk amm amo amr ams aoa aob aoe aok aom aoo aor aos ar- ara arb are ark arm aro arr ars as- asa asb ase ask asm aso asr ass baa bab bae bak bam bao bar bas bba bbb bbe bbk bbm bbo bbr bbs be- bea beb bee bek bem beo ber bes bka bkb bke bkk bkm bko bkr bks bma bmb bme bmk bmm bmo bmr bms boa bob boe bok bom boo bor bos bra brb bre brk brm bro brr brs bsa bsb bse bsk bsm bso bsr bss eaa eab eae eak eam eao ear eas eba ebb ebe ebk ebm ebo ebr ebs eea eeb eee eek eem eeo eer ees eka ekb eke eko ekr eks em- ema emb eme emk emm emo emr ems eo- eoa eob eoe eok eom eoo eor eos era erb ere erk erm ero err ers es- esa esb ese esk esm eso esr ess ka- kaa kab kae kak kam kao kar kas kba kbb kbe kbk kbm kbo kbr kbs ke- kea keb kee kek kem keo ker kes kkb kke kkk kkm kkr kks kma kmb kme kmk kmm kmo kms koa kob koe kok kom koo kor kos kra krk kro krr krs ksa ksb kse ksk ksm kso ksr kss m-o m-r maa mab mae mak mam mao mar mas mba mbb mbe mbk mbm mbo mbr mbs mea meb mee mek mem meo mer mes mka mkb mke mkk mkm mko mkr mks mma mmb mme mmk mmm mmo mmr mms moa mob moe mok mom moo mor mos mra mrb mre mrk mrm mro mrr mrs msa msb mse msk msm mso msr mss oaa oab oae oak oam oao oar oas ob- oba obb obe obk obm obo obr obs oea oeb oee oem oeo oer oes oka okb oke okk oko okr oks om- oma omb ome omm omo omr oms oo- ooa oob ook oom ooo oor oos or- ora orb ore ork orm oro orr ors os- osa osb ose osk osm oso osr oss ra- raa rab rae rak ram rao rar ras rba rbb rbe rbk rbm rbo rbr rbs re- rea reb ree rek rem reo rer res rkb rke rkk rkm rko rks rma rmb rme rmm rmo rmr rms roa rob roe rok rom roo ror ros rra rrb rrk rrm rrr rrs rsa rsb rse rsk rsm rso rsr rss saa sab sae sak sam sao sar sas sba sbb sbe sbk sbm sbo sbr sbs se- sea seb see sek sem seo ser ses sk- ska skb ske skk skm sko skr sks sma smb sme smk smm smo smr sms soa sob soe sok som soo sor sos sr- sra srb sre srk srm sro srr srs ss- ssa ssb sse ssk ssm sso ssr sss