a-a a-c aaa aac aaf aak aao aar ac- aca acc acf ack aco acr af- afa afc aff afk afo afr aka akc akk ako akr aoa aoc aof aok aoo aor ar- ara arc arf ark aro arr c-- caa cac caf cak cao car cca ccc ccf cck cco ccr cfa cfc cff cfk cfo cfr cka ckc cko co- coa coc cof cok coo cor cra crc crf crk cro crr faa fac faf fak fao far fca fcc fcf fck fco fcr ffa ffc fff ffk ffo ffr fka fkc fkf fkk foa foc fof fok foo for fra frc frf frk fro frr ka- kaa kac kaf kak kao kar kca kcc kck kcr kfa kfc kff kfo kkc kkk kkr koa koc kof kok koo kor kra krc krf krk kro krr oaa oac oaf oak oao oar oc- oca occ ocf ock oco ocr of- ofa ofc off ofo ofr oka okc okk oko okr oo- ooa ooc oof ook ooo oor or- ora orc orf ork oro orr ra- raa rac raf rak rao rar rca rcc rcf rco rcr rfa rfc rff rfk rfo rfr rkc rkf rkk rko roa roc rof rok roo ror rra rrc rrf rrk rrr