-er c-- ccc cce cco ccr ccx ce- cec cee ceo cer cex co- coc coe coo cor cox crc cre cro crr crx cxc cxo cxr cxx ec- ecc ece eco ecr ecx eec eee eeo eer eex eo- eoc eoe eoo eor erc ere ero err ex- exc exe exo exr exx oc- occ oco ocr ocx oec oee oeo oer oex oo- ooc ooo oor oox or- orc ore oro orr orx ox- oxc oxo oxx rcc rce rco rcr rcx re- rec ree reo rer rex roc roe roo ror rox rrc rrr rxr xcr xcx xee xer xex xoc xoo xor xox xrc xrx xxo xxx