-er a-a a-b a-i aaa aab aae aag aai aao aar aax ab- aba abb abe abg abi abo abr abx aea aeb aee aeg aei aeo aer aex ag- aga agb age agg agi ago agr agx ai- aia aib aie aig aii aio air aix aoa aob aoe aog aoi aoo aor aox ar- ara arb are arg ari aro arr arx ax- axa axe axi axo axr axx baa bab bae bag bai bao bar bax bba bbb bbe bbg bbi bbo bbr bbx be- bea beb bee beg bei beo ber bex bga bgb bge bgg bgi bgo bgr bgx bi- bia bib bie big bii bio bir bix boa bob boe bog boi boo bor box bra brb bre brg bri bro brr brx bxb bxi bxo bxx eaa eab eae eag eai eao ear eax eba ebb ebe ebg ebi ebo ebr ebx eea eeb eee eeg eeo eer eex ega egb ege egg egi ego egr egx eia eib eie eig eii eio eir eix eo- eoa eob eoe eog eoi eoo eor era erb ere erg eri ero err ex- exa exe exi exo exr exx gaa gab gae gag gai gao gar gba gbe gbg gbi gbo gbr gbx ge- gea geb gee geg gei geo ger gex gga ggb ggg ggi ggo ggr gia gib gie gig gii gio gir goa gob goe gog goi goo gor gox gra grb gre grg gri gro grr grx gxa ia- iaa iab iae iag iai iao iar iba ibb ibe ibg ibi ibo ibr ibx ie- iea iee ieg iei ier iex iga igb ige igg igi igo igr iia iib iie iii iio iir iix io- ioa iob ioe iog ioi ioo ior ir- ira irb ire irg iri iro irr irx ixe ixi o-i oaa oab oae oag oai oao oar oax ob- oba obb obe obg obi obo obr obx oea oeb oee oeg oei oeo oer oex oga oge ogg ogi ogo ogx oia oib oie oii oio oir oo- ooa oob oog ooi ooo oor oox or- ora orb ore org ori oro orr orx ox- oxa oxb oxi oxo oxx ra- raa rab rae rag rai rao rar rax rba rbb rbe rbg rbi rbo rbr rbx re- rea reb ree reg rei reo rer rex rga rgb rge rgg rgi rgo rgr rgx ria rib rie rig rii rio rir rix roa rob roe rog roi roo ror rox rra rrb rrg rri rrr rxr xaa xag xar xbe xbr xbx xee xeg xer xex xge xgi xia xie xii xio xix xoa xog xoi xoo xor xox xrx xxi xxo xxx