-er c-- ccc cce ccf cck cco ccr ccs ce- cec cee cef cek ceo cer ces cfc cfe cff cfk cfo cfr cfs ckc cko cks co- coc coe cof cok coo cor cos crc cre crf crk cro crr crs csc cse csf csk cso csr css ec- ecc ece ecf eck eco ecr ecs eec eee eef eek eeo eer ees ef- efc efe eff efo efr efs ekc eke ekf eko ekr eks eo- eoc eoe eof eok eoo eor eos erc ere erf erk ero err ers es- esc ese esf esk eso esr ess fcc fce fcf fck fco fcr fcs fec fee fef fek feo fer fes ffc ffe fff ffk ffo ffr ffs fkc fkf fkk foc foe fof fok foo for fos frc fre frf frk fro frr frs fsc fse fsf fsk fso fsr fss kcc kce kck kcr kcs ke- kec kee kef kek keo ker kes kfc kff kfo kfs kkc kke kkk kkr kks koc koe kof kok koo kor kos krc krf krk kro krr krs ksc kse ksf ksk kso ksr kss oc- occ ocf ock oco ocr ocs oec oee oef oeo oer oes of- ofc ofe off ofo ofr ofs okc oke okk oko okr oks oo- ooc oof ook ooo oor oos or- orc ore orf ork oro orr ors os- osc ose osf osk oso osr oss rcc rce rcf rco rcr rcs re- rec ree ref rek reo rer res rfc rfe rff rfk rfo rfr rfs rkc rke rkf rkk rko rks roc roe rof rok roo ror ros rrc rrf rrk rrr rrs rsc rse rsf rsk rso rsr rss scc sce scf sck sco scr scs se- sec see sef sek seo ser ses sfc sfe sff sfk sfo sfr sfs sk- skc ske skf skk sko skr sks soc soe sof sok soo sor sos sr- src sre srf srk sro srr srs ss- ssc sse ssf ssk sso ssr sss