-er a-a a-c aaa aac aae aao aar aax ac- aca acc ace aco acr acx aea aec aee aeo aer aex aoa aoc aoe aoo aor aox ar- ara arc are aro arr arx ax- axa axe axo axr axx c-- caa cac cae cao car cax cca ccc cce cco ccr ccx ce- cea cec cee ceo cer cex co- coa coc coe coo cor cox cra crc cre cro crr crx cxc cxo cxr cxx eaa eac eae eao ear eax ec- eca ecc ece eco ecr ecx eea eec eee eeo eer eex eo- eoa eoc eoe eoo eor era erc ere ero err ex- exa exc exe exo exr exx oaa oac oae oao oar oax oc- oca occ oco ocr ocx oea oec oee oeo oer oex oo- ooa ooc ooo oor oox or- ora orc ore oro orr orx ox- oxa oxc oxo oxx ra- raa rac rae rao rar rax rca rcc rce rco rcr rcx re- rea rec ree reo rer rex roa roc roe roo ror rox rra rrc rrr rxr xaa xac xar xcr xcx xee xer xex xoa xoc xoo xor xox xrc xrx xxo xxx