-er a-a a-b a-i a-t aaa aab aae aai aao aar aat aax ab- aba abb abe abi abo abr abt abx aea aeb aee aei aeo aer aet aex ai- aia aib aie aii aio air ait aix aoa aob aoe aoi aoo aor aot aox ar- ara arb are ari aro arr art arx at- ata atb ate ati ato atr att atx ax- axa axe axi axo axr axt axx baa bab bae bai bao bar bat bax bba bbb bbe bbi bbo bbr bbt bbx be- bea beb bee bei beo ber bet bex bi- bia bib bie bii bio bir bit bix boa bob boe boi boo bor bot box bra brb bre bri bro brr brt brx bta btb bte bti bto btr btt btx bxb bxi bxo bxx eaa eab eae eai eao ear eat eax eba ebb ebe ebi ebo ebr ebt ebx eea eeb eee eeo eer eet eex eia eib eie eii eio eir eit eix eo- eoa eob eoe eoi eoo eor eot era erb ere eri ero err ert eta etb ete eti eto etr ett etx ex- exa exe exi exo exr ext exx ia- iaa iab iae iai iao iar iat iba ibb ibe ibi ibo ibr ibt ibx ie- iea iee iei ier iet iex iia iib iie iii iio iir iit iix io- ioa iob ioe ioi ioo ior iot ir- ira irb ire iri iro irr irt irx ita itb ite iti ito itt itx ixe ixi o-i oaa oab oae oai oao oar oat oax ob- oba obb obe obi obo obr obt obx oea oeb oee oei oeo oer oet oex oia oib oie oii oio oir oit oo- ooa oob ooi ooo oor oot oox or- ora orb ore ori oro orr ort orx ot- ota otb ote oti oto otr ott ox- oxa oxb oxi oxo oxt oxx ra- raa rab rae rai rao rar rat rax rba rbb rbe rbi rbo rbr rbt rbx re- rea reb ree rei reo rer ret rex ria rib rie rii rio rir rit rix roa rob roe roi roo ror rot rox rra rrb rri rrr rrt rta rtb rte rti rto rtr rtt rtx rxr t-x taa tab tae tai tao tar tat tax tba tbb tbe tbi tbo tbr tbt te- tea teb tee tei teo ter tet tex tia tib tie tii tio tir tit tix to- toa tob toe toi too tor tot tox tra trb tre tri tro trr trt trx tta ttb tte tti tto ttr ttt ttx txe txi txt xaa xar xat xbe xbr xbx xee xer xet xex xia xie xii xio xit xix xoa xoi xoo xor xot xox xrt xrx xti xtr xtx xxi xxo xxx