-er c-- ccc cce cco ccr ccs ccx ce- cec cee ceo cer ces cex co- coc coe coo cor cos cox crc cre cro crr crs crx csc cse cso csr css csx cxc cxo cxr cxs cxx ec- ecc ece eco ecr ecs ecx eec eee eeo eer ees eex eo- eoc eoe eoo eor eos erc ere ero err ers es- esc ese eso esr ess esx ex- exc exe exo exr exs exx oc- occ oco ocr ocs ocx oec oee oeo oer oes oex oo- ooc ooo oor oos oox or- orc ore oro orr ors orx os- osc ose oso osr oss osx ox- oxc oxo oxx rcc rce rco rcr rcs rcx re- rec ree reo rer res rex roc roe roo ror ros rox rrc rrr rrs rsc rse rso rsr rss rsx rxr rxs scc sce sco scr scs scx se- sec see seo ser ses sex soc soe soo sor sos sox sr- src sre sro srr srs srx ss- ssc sse sso ssr sss ssx sxc sxs xcr xcx xee xer xes xex xoc xoo xor xos xox xrc xrx xsc xss xxo xxx