-er a-a a-c aaa aac aae aak aar ac- aca acc ace ack acr aea aec aee aek aer aka akc ake akk akr ar- ara arc are ark arr c-- caa cac cae cak car cca ccc cce cck ccr ce- cea cec cee cek cer cka ckc cra crc cre crk crr eaa eac eae eak ear ec- eca ecc ece eck ecr eea eec eee eek eer eka ekc eke ekr era erc ere erk err ka- kaa kac kae kak kar kca kcc kce kck kcr ke- kea kec kee kek ker kkc kke kkk kkr kra krc krk krr ra- raa rac rae rak rar rca rcc rce rcr re- rea rec ree rek rer rkc rke rkk rra rrc rrk rrr