-er c-- ccc cce ccn cco ccr ccx ce- cec cee cen ceo cer cex cn- cnc cne cnn cno cnr cnx co- coc coe con coo cor cox crc cre crn cro crr crx cxc cxo cxr cxx ec- ecc ece ecn eco ecr ecx eec eee een eeo eer eex en- enc ene enn eno enr eo- eoc eoe eon eoo eor erc ere ern ero err ex- exc exe exo exr exx ncc nce ncn nco ncr ncx ne- nec nee nen neo ner nex nnc nne nnn nno no- noc noe non noo nor nox nrc nre nrn nro nrr nrx nxc oc- occ ocn oco ocr ocx oec oee oen oeo oer oex on- onc one onn ono onr onx oo- ooc oon ooo oor oox or- orc ore orn oro orr orx ox- oxc oxn oxo oxx rcc rce rcn rco rcr rcx re- rec ree ren reo rer rex rnc rnn rno rnr roc roe ron roo ror rox rrc rrn rrr rxr xcr xcx xee xen xer xex xnc xno xoc xon xoo xor xox xrc xrx xxo xxx