a-a a-b aaa aab aak aam aao aar aas ab- aba abb abk abm abo abr abs aka akb akk akm ako akr aks ama amb amk amm amo amr ams aoa aob aok aom aoo aor aos ar- ara arb ark arm aro arr ars as- asa asb ask asm aso asr ass baa bab bak bam bao bar bas bba bbb bbk bbm bbo bbr bbs bka bkb bkk bkm bko bkr bks bma bmb bmk bmm bmo bmr bms boa bob bok bom boo bor bos bra brb brk brm bro brr brs bsa bsb bsk bsm bso bsr bss ka- kaa kab kak kam kao kar kas kba kbb kbk kbm kbo kbr kbs kkb kkk kkm kkr kks kma kmb kmk kmm kmo kms koa kob kok kom koo kor kos kra krk kro krr krs ksa ksb ksk ksm kso ksr kss m-o m-r maa mab mak mam mao mar mas mba mbb mbk mbm mbo mbr mbs mka mkb mkk mkm mko mkr mks mma mmb mmk mmm mmo mmr mms moa mob mok mom moo mor mos mra mrb mrk mrm mro mrr mrs msa msb msk msm mso msr mss oaa oab oak oam oao oar oas ob- oba obb obk obm obo obr obs oka okb okk oko okr oks om- oma omb omm omo omr oms oo- ooa oob ook oom ooo oor oos or- ora orb ork orm oro orr ors os- osa osb osk osm oso osr oss ra- raa rab rak ram rao rar ras rba rbb rbk rbm rbo rbr rbs rkb rkk rkm rko rks rma rmb rmm rmo rmr rms roa rob rok rom roo ror ros rra rrb rrk rrm rrr rrs rsa rsb rsk rsm rso rsr rss saa sab sak sam sao sar sas sba sbb sbk sbm sbo sbr sbs sk- ska skb skk skm sko skr sks sma smb smk smm smo smr sms soa sob sok som soo sor sos sr- sra srb srk srm sro srr srs ss- ssa ssb ssk ssm sso ssr sss