-er a-a a-b a-t aaa aab aae aaf aao aar aat aax ab- aba abb abe abf abo abr abt abx aea aeb aee aef aeo aer aet aex af- afa afb afe aff afo afr aft afx aoa aob aoe aof aoo aor aot aox ar- ara arb are arf aro arr art arx at- ata atb ate atf ato atr att atx ax- axa axe axo axr axt axx baa bab bae baf bao bar bat bax bba bbb bbe bbf bbo bbr bbt bbx be- bea beb bee bef beo ber bet bex bfa bfb bfe bff bfo bfr bft bfx boa bob boe bof boo bor bot box bra brb bre brf bro brr brt brx bta btb bte btf bto btr btt btx bxb bxo bxx eaa eab eae eaf eao ear eat eax eba ebb ebe ebf ebo ebr ebt ebx eea eeb eee eef eeo eer eet eex ef- efa efb efe eff efo efr eft efx eo- eoa eob eoe eof eoo eor eot era erb ere erf ero err ert eta etb ete etf eto etr ett etx ex- exa exe exo exr ext exx faa fab fae faf fao far fat fax fba fbb fbe fbf fbo fbr fbt fbx fea feb fee fef feo fer fet fex ffa ffe fff ffo ffr fft ffx foa fob foe fof foo for fot fox fra frb fre frf fro frr frt fta ftb fte ftf fto ftr ftt ftx fxe fxr fxt fxx oaa oab oae oaf oao oar oat oax ob- oba obb obe obf obo obr obt obx oea oeb oee oef oeo oer oet oex of- ofa ofb ofe off ofo ofr oft ofx oo- ooa oob oof ooo oor oot oox or- ora orb ore orf oro orr ort orx ot- ota otb ote otf oto otr ott ox- oxa oxb oxf oxo oxt oxx ra- raa rab rae raf rao rar rat rax rba rbb rbe rbf rbo rbr rbt rbx re- rea reb ree ref reo rer ret rex rfa rfb rfe rff rfo rfr rft roa rob roe rof roo ror rot rox rra rrb rrf rrr rrt rta rtb rte rtf rto rtr rtt rtx rxr t-x taa tab tae taf tao tar tat tax tba tbb tbe tbf tbo tbr tbt te- tea teb tee tef teo ter tet tex tfa tfb tfe tff tfo tfr tft tfx to- toa tob toe tof too tor tot tox tra trb tre trf tro trr trt trx tta ttb tte ttf tto ttr ttt ttx txe txf txt xaa xaf xar xat xbe xbr xbx xee xer xet xex xfa xfe xft xfx xoa xof xoo xor xot xox xrf xrt xrx xtf xtr xtx xxo xxx