-er a-a a-c aaa aac aae aak aar aas ac- aca acc ace ack acr acs aea aec aee aek aer aes aka akc ake akk akr aks ar- ara arc are ark arr ars as- asa asc ase ask asr ass c-- caa cac cae cak car cas cca ccc cce cck ccr ccs ce- cea cec cee cek cer ces cka ckc cks cra crc cre crk crr crs csa csc cse csk csr css eaa eac eae eak ear eas ec- eca ecc ece eck ecr ecs eea eec eee eek eer ees eka ekc eke ekr eks era erc ere erk err ers es- esa esc ese esk esr ess ka- kaa kac kae kak kar kas kca kcc kce kck kcr kcs ke- kea kec kee kek ker kes kkc kke kkk kkr kks kra krc krk krr krs ksa ksc kse ksk ksr kss ra- raa rac rae rak rar ras rca rcc rce rcr rcs re- rea rec ree rek rer res rkc rke rkk rks rra rrc rrk rrr rrs rsa rsc rse rsk rsr rss saa sac sae sak sar sas sca scc sce sck scr scs se- sea sec see sek ser ses sk- ska skc ske skk skr sks sr- sra src sre srk srr srs ss- ssa ssc sse ssk ssr sss