a-a a-c aaa aac aaf aak aar ac- aca acc acf ack acr af- afa afc aff afk afr aka akc akk akr ar- ara arc arf ark arr c-- caa cac caf cak car cca ccc ccf cck ccr cfa cfc cff cfk cfr cka ckc cra crc crf crk crr faa fac faf fak far fca fcc fcf fck fcr ffa ffc fff ffk ffr fka fkc fkf fkk fra frc frf frk frr ka- kaa kac kaf kak kar kca kcc kck kcr kfa kfc kff kkc kkk kkr kra krc krf krk krr ra- raa rac raf rak rar rca rcc rcf rcr rfa rfc rff rfk rfr rkc rkf rkk rra rrc rrf rrk rrr