-er c-- ccc ccd cce cck cco ccr ccx cdc cdd cde cdk cdo cdr cdx ce- cec ced cee cek ceo cer cex ckc ckd cko ckx co- coc cod coe cok coo cor cox crc crd cre crk cro crr crx cxc cxk cxo cxr cxx dcc dcd dce dck dco dcr dcx ddc ddd dde ddk ddo ddr ddx de- dec ded dee dek deo der dex dkc dke dkk dko dkr dkx doc dod doe dok doo dor dox drc drd dre drk dro drr drx dxc dxd dxo dxr dxx ec- ecc ecd ece eck eco ecr ecx ed- edc edd ede edk edo edr edx eec eed eee eek eeo eer eex ekc ekd eke eko ekr eo- eoc eod eoe eok eoo eor erc erd ere erk ero err ex- exc exd exe exo exr exx kcc kcd kce kck kcr kcx kdc kde kdk kdo kdr kdx ke- kec ked kee kek keo ker kex kkc kke kkk kkr koc kod koe kok koo kor krc krd krk kro krr kxo oc- occ ocd ock oco ocr ocx odc odd ode odo odr oec oed oee oeo oer oex okc okd oke okk oko okr oo- ooc ood ook ooo oor oox or- orc ord ore ork oro orr orx ox- oxc oxo oxx rcc rcd rce rco rcr rcx rdc rdd rde rdo rdr rdx re- rec red ree rek reo rer rex rkc rke rkk rko roc rod roe rok roo ror rox rrc rrd rrk rrr rxr xcd xcr xcx xdc xde xdk xdr xed xee xer xex xke xoc xod xok xoo xor xox xrc xrd xrx xxo xxx