a-a a-c aaa aac aad aaf aak aao ac- aca acc acd acf ack aco ad- ada adc add adf adk ado af- afa afc afd aff afk afo aka akc akd akk ako aoa aoc aod aof aok aoo c-- caa cac cad caf cak cao cca ccc ccd ccf cck cco cda cdc cdd cdf cdk cdo cfa cfc cfd cff cfk cfo cka ckc ckd cko co- coa coc cod cof cok coo daa dac dad daf dak dao dca dcc dcd dcf dck dco dda ddc ddd ddf ddk ddo dfa dfc dfd dff dfk dfo dka dkc dkk dko doa doc dod dof dok doo faa fac fad faf fak fao fca fcc fcd fcf fck fco fda fdc fdd fdf fdk fdo ffa ffc ffd fff ffk ffo fka fkc fkf fkk foa foc fof fok foo ka- kaa kac kad kaf kak kao kca kcc kcd kck kda kdc kdf kdk kdo kfa kfc kfd kff kfo kkc kkk koa koc kod kof kok koo oaa oac oad oaf oak oao oc- oca occ ocd ocf ock oco oda odc odd odf odo of- ofa ofc ofd off ofo oka okc okd okk oko oo- ooa ooc ood oof ook ooo