-er a-a a-b a-c a-t aaa aab aac aae aao aar aat aax ab- aba abb abc abe abo abr abt abx ac- aca acb acc ace aco acr act acx aea aeb aec aee aeo aer aet aex aoa aob aoc aoe aoo aor aot aox ar- ara arb arc are aro arr art arx at- ata atb atc ate ato atr att atx ax- axa axe axo axr axt axx baa bab bac bae bao bar bat bax bba bbb bbc bbe bbo bbr bbt bbx bca bcb bcc bce bco bcr bct bcx be- bea beb bec bee beo ber bet bex boa bob boc boe boo bor bot box bra brb bre bro brr brt brx bta btb btc bte bto btr btt btx bxb bxo bxx c-- caa cab cac cae cao car cat cax cba cbb cbc cbe cbo cbr cbt cbx cca ccb ccc cce cco ccr cct ccx ce- cea ceb cec cee ceo cer cet cex co- coa cob coc coe coo cor cot cox cra crb crc cre cro crr crt crx cta ctb ctc cte cto ctr ctt ctx cxc cxo cxr cxt cxx eaa eab eac eae eao ear eat eax eba ebb ebc ebe ebo ebr ebt ebx ec- eca ecb ecc ece eco ecr ect ecx eea eeb eec eee eeo eer eet eex eo- eoa eob eoc eoe eoo eor eot era erb erc ere ero err ert eta etb etc ete eto etr ett etx ex- exa exc exe exo exr ext exx oaa oab oac oae oao oar oat oax ob- oba obb obc obe obo obr obt obx oc- oca ocb occ oco ocr oct ocx oea oeb oec oee oeo oer oet oex oo- ooa oob ooc ooo oor oot oox or- ora orb orc ore oro orr ort orx ot- ota otb otc ote oto otr ott ox- oxa oxb oxc oxo oxt oxx ra- raa rab rac rae rao rar rat rax rba rbb rbc rbe rbo rbr rbt rbx rca rcb rcc rce rco rcr rct rcx re- rea reb rec ree reo rer ret rex roa rob roc roe roo ror rot rox rra rrb rrc rrr rrt rta rtb rtc rte rto rtr rtt rtx rxr t-x taa tab tac tae tao tar tat tax tba tbb tbc tbe tbo tbr tbt tca tcb tcc tce tco tcr tct tcx te- tea teb tec tee teo ter tet tex to- toa tob toc toe too tor tot tox tra trb trc tre tro trr trt trx tta ttb ttc tte tto ttr ttt ttx txe txt xaa xac xar xat xbc xbe xbr xbx xcb xcr xcx xee xer xet xex xoa xoc xoo xor xot xox xrc xrt xrx xtc xtr xtx xxo xxx