a-a a-b aaa aab aak aam aao aas ab- aba abb abk abm abo abs aka akb akk akm ako aks ama amb amk amm amo ams aoa aob aok aom aoo aos as- asa asb ask asm aso ass baa bab bak bam bao bas bba bbb bbk bbm bbo bbs bka bkb bkk bkm bko bks bma bmb bmk bmm bmo bms boa bob bok bom boo bos bsa bsb bsk bsm bso bss ka- kaa kab kak kam kao kas kba kbb kbk kbm kbo kbs kkb kkk kkm kks kma kmb kmk kmm kmo kms koa kob kok kom koo kos ksa ksb ksk ksm kso kss m-o maa mab mak mam mao mas mba mbb mbk mbm mbo mbs mka mkb mkk mkm mko mks mma mmb mmk mmm mmo mms moa mob mok mom moo mos msa msb msk msm mso mss oaa oab oak oam oao oas ob- oba obb obk obm obo obs oka okb okk oko oks om- oma omb omm omo oms oo- ooa oob ook oom ooo oos os- osa osb osk osm oso oss saa sab sak sam sao sas sba sbb sbk sbm sbo sbs sk- ska skb skk skm sko sks sma smb smk smm smo sms soa sob sok som soo sos ss- ssa ssb ssk ssm sso sss