-er c-- ccc cce cco ccr cct ccx ce- cec cee ceo cer cet cex co- coc coe coo cor cot cox crc cre cro crr crt crx ctc cte cto ctr ctt ctx cxc cxo cxr cxt cxx ec- ecc ece eco ecr ect ecx eec eee eeo eer eet eex eo- eoc eoe eoo eor eot erc ere ero err ert etc ete eto etr ett etx ex- exc exe exo exr ext exx oc- occ oco ocr oct ocx oec oee oeo oer oet oex oo- ooc ooo oor oot oox or- orc ore oro orr ort orx ot- otc ote oto otr ott ox- oxc oxo oxt oxx rcc rce rco rcr rct rcx re- rec ree reo rer ret rex roc roe roo ror rot rox rrc rrr rrt rtc rte rto rtr rtt rtx rxr t-x tcc tce tco tcr tct tcx te- tec tee teo ter tet tex to- toc toe too tor tot tox trc tre tro trr trt trx ttc tte tto ttr ttt ttx txe txt xcr xcx xee xer xet xex xoc xoo xor xot xox xrc xrt xrx xtc xtr xtx xxo xxx