-er a-a a-c aaa aac aae aaf aak aar ac- aca acc ace acf ack acr aea aec aee aef aek aer af- afa afc afe aff afk afr aka akc ake akk akr ar- ara arc are arf ark arr c-- caa cac cae caf cak car cca ccc cce ccf cck ccr ce- cea cec cee cef cek cer cfa cfc cfe cff cfk cfr cka ckc cra crc cre crf crk crr eaa eac eae eaf eak ear ec- eca ecc ece ecf eck ecr eea eec eee eef eek eer ef- efa efc efe eff efr eka ekc eke ekf ekr era erc ere erf erk err faa fac fae faf fak far fca fcc fce fcf fck fcr fea fec fee fef fek fer ffa ffc ffe fff ffk ffr fka fkc fkf fkk fra frc fre frf frk frr ka- kaa kac kae kaf kak kar kca kcc kce kck kcr ke- kea kec kee kef kek ker kfa kfc kff kkc kke kkk kkr kra krc krf krk krr ra- raa rac rae raf rak rar rca rcc rce rcf rcr re- rea rec ree ref rek rer rfa rfc rfe rff rfk rfr rkc rke rkf rkk rra rrc rrf rrk rrr