-er a-a a-b aaa aab aae aag aao aar aax ab- aba abb abe abg abo abr abx aea aeb aee aeg aeo aer aex ag- aga agb age agg ago agr agx aoa aob aoe aog aoo aor aox ar- ara arb are arg aro arr arx ax- axa axe axo axr axx baa bab bae bag bao bar bax bba bbb bbe bbg bbo bbr bbx be- bea beb bee beg beo ber bex bga bgb bge bgg bgo bgr bgx boa bob boe bog boo bor box bra brb bre brg bro brr brx bxb bxo bxx eaa eab eae eag eao ear eax eba ebb ebe ebg ebo ebr ebx eea eeb eee eeg eeo eer eex ega egb ege egg ego egr egx eo- eoa eob eoe eog eoo eor era erb ere erg ero err ex- exa exe exo exr exx gaa gab gae gag gao gar gba gbe gbg gbo gbr gbx ge- gea geb gee geg geo ger gex gga ggb ggg ggo ggr goa gob goe gog goo gor gox gra grb gre grg gro grr grx gxa oaa oab oae oag oao oar oax ob- oba obb obe obg obo obr obx oea oeb oee oeg oeo oer oex oga oge ogg ogo ogx oo- ooa oob oog ooo oor oox or- ora orb ore org oro orr orx ox- oxa oxb oxo oxx ra- raa rab rae rag rao rar rax rba rbb rbe rbg rbo rbr rbx re- rea reb ree reg reo rer rex rga rgb rge rgg rgo rgr rgx roa rob roe rog roo ror rox rra rrb rrg rrr rxr xaa xag xar xbe xbr xbx xee xeg xer xex xge xoa xog xoo xor xox xrx xxo xxx