-er c-- ccc cce ccg cco ccr ccs ce- cec cee ceg ceo cer ces cgc cge cgg cgo cgr cgs co- coc coe cog coo cor cos crc cre crg cro crr crs csc cse csg cso csr css ec- ecc ece ecg eco ecr ecs eec eee eeg eeo eer ees egc ege egg ego egr egs eo- eoc eoe eog eoo eor eos erc ere erg ero err ers es- esc ese esg eso esr ess gcc gce gcg gco gcr gcs ge- gec gee geg geo ger ges ggc ggg ggo ggr ggs goc goe gog goo gor gos grc gre grg gro grr grs gsc gse gsg gso gsr gss oc- occ ocg oco ocr ocs oec oee oeg oeo oer oes ogc oge ogg ogo ogs oo- ooc oog ooo oor oos or- orc ore org oro orr ors os- osc ose osg oso osr oss rcc rce rcg rco rcr rcs re- rec ree reg reo rer res rgc rge rgg rgo rgr rgs roc roe rog roo ror ros rrc rrg rrr rrs rsc rse rsg rso rsr rss scc sce scg sco scr scs se- sec see seg seo ser ses sgc sge sgg sgo sgr sgs soc soe sog soo sor sos sr- src sre srg sro srr srs ss- ssc sse ssg sso ssr sss