-er c-- ccc cce ccm cco ccr ccs ce- cec cee cem ceo cer ces cmc cme cmm cmo cmr cms co- coc coe com coo cor cos crc cre crm cro crr crs csc cse csm cso csr css ec- ecc ece ecm eco ecr ecs eec eee eem eeo eer ees em- emc eme emm emo emr ems eo- eoc eoe eom eoo eor eos erc ere erm ero err ers es- esc ese esm eso esr ess m-o m-r mc- mcc mce mcm mco mcr mcs mec mee mem meo mer mes mmc mme mmm mmo mmr mms moc moe mom moo mor mos mrc mre mrm mro mrr mrs msc mse msm mso msr mss oc- occ ocm oco ocr ocs oec oee oem oeo oer oes om- omc ome omm omo omr oms oo- ooc oom ooo oor oos or- orc ore orm oro orr ors os- osc ose osm oso osr oss rcc rce rcm rco rcr rcs re- rec ree rem reo rer res rmc rme rmm rmo rmr rms roc roe rom roo ror ros rrc rrm rrr rrs rsc rse rsm rso rsr rss scc sce scm sco scr scs se- sec see sem seo ser ses smc sme smm smo smr sms soc soe som soo sor sos sr- src sre srm sro srr srs ss- ssc sse ssm sso ssr sss