-er a-a a-b a-t aaa aab aae aao aar aat aax ab- aba abb abe abo abr abt abx aea aeb aee aeo aer aet aex aoa aob aoe aoo aor aot aox ar- ara arb are aro arr art arx at- ata atb ate ato atr att atx ax- axa axe axo axr axt axx baa bab bae bao bar bat bax bba bbb bbe bbo bbr bbt bbx be- bea beb bee beo ber bet bex boa bob boe boo bor bot box bra brb bre bro brr brt brx bta btb bte bto btr btt btx bxb bxo bxx eaa eab eae eao ear eat eax eba ebb ebe ebo ebr ebt ebx eea eeb eee eeo eer eet eex eo- eoa eob eoe eoo eor eot era erb ere ero err ert eta etb ete eto etr ett etx ex- exa exe exo exr ext exx oaa oab oae oao oar oat oax ob- oba obb obe obo obr obt obx oea oeb oee oeo oer oet oex oo- ooa oob ooo oor oot oox or- ora orb ore oro orr ort orx ot- ota otb ote oto otr ott ox- oxa oxb oxo oxt oxx ra- raa rab rae rao rar rat rax rba rbb rbe rbo rbr rbt rbx re- rea reb ree reo rer ret rex roa rob roe roo ror rot rox rra rrb rrr rrt rta rtb rte rto rtr rtt rtx rxr t-x taa tab tae tao tar tat tax tba tbb tbe tbo tbr tbt te- tea teb tee teo ter tet tex to- toa tob toe too tor tot tox tra trb tre tro trr trt trx tta ttb tte tto ttr ttt ttx txe txt xaa xar xat xbe xbr xbx xee xer xet xex xoa xoo xor xot xox xrt xrx xtr xtx xxo xxx