-er c-- ccc cce cck cco ccr ccs ce- cec cee cek ceo cer ces ckc cko cks co- coc coe cok coo cor cos crc cre crk cro crr crs csc cse csk cso csr css ec- ecc ece eck eco ecr ecs eec eee eek eeo eer ees ekc eke eko ekr eks eo- eoc eoe eok eoo eor eos erc ere erk ero err ers es- esc ese esk eso esr ess kcc kce kck kcr kcs ke- kec kee kek keo ker kes kkc kke kkk kkr kks koc koe kok koo kor kos krc krk kro krr krs ksc kse ksk kso ksr kss oc- occ ock oco ocr ocs oec oee oeo oer oes okc oke okk oko okr oks oo- ooc ook ooo oor oos or- orc ore ork oro orr ors os- osc ose osk oso osr oss rcc rce rco rcr rcs re- rec ree rek reo rer res rkc rke rkk rko rks roc roe rok roo ror ros rrc rrk rrr rrs rsc rse rsk rso rsr rss scc sce sck sco scr scs se- sec see sek seo ser ses sk- skc ske skk sko skr sks soc soe sok soo sor sos sr- src sre srk sro srr srs ss- ssc sse ssk sso ssr sss