-er a-a a-c aaa aac aae aaf aao aar aax ac- aca acc ace acf aco acr acx aea aec aee aef aeo aer aex af- afa afc afe aff afo afr afx aoa aoc aoe aof aoo aor aox ar- ara arc are arf aro arr arx ax- axa axe axo axr axx c-- caa cac cae caf cao car cax cca ccc cce ccf cco ccr ccx ce- cea cec cee cef ceo cer cex cfa cfc cfe cff cfo cfr cfx co- coa coc coe cof coo cor cox cra crc cre crf cro crr crx cxc cxf cxo cxr cxx eaa eac eae eaf eao ear eax ec- eca ecc ece ecf eco ecr ecx eea eec eee eef eeo eer eex ef- efa efc efe eff efo efr efx eo- eoa eoc eoe eof eoo eor era erc ere erf ero err ex- exa exc exe exo exr exx faa fac fae faf fao far fax fca fcc fce fcf fco fcr fcx fea fec fee fef feo fer fex ffa ffc ffe fff ffo ffr ffx foa foc foe fof foo for fox fra frc fre frf fro frr fxe fxr fxx oaa oac oae oaf oao oar oax oc- oca occ ocf oco ocr ocx oea oec oee oef oeo oer oex of- ofa ofc ofe off ofo ofr ofx oo- ooa ooc oof ooo oor oox or- ora orc ore orf oro orr orx ox- oxa oxc oxf oxo oxx ra- raa rac rae raf rao rar rax rca rcc rce rcf rco rcr rcx re- rea rec ree ref reo rer rex rfa rfc rfe rff rfo rfr roa roc roe rof roo ror rox rra rrc rrf rrr rxr xaa xac xaf xar xcf xcr xcx xee xer xex xfa xfe xfx xoa xoc xof xoo xor xox xrc xrf xrx xxo xxx