-er a-a a-b a-i aaa aab aad aae aag aai aar aax ab- aba abb abd abe abg abi abr abx ad- ada adb add ade adg adi adr adx aea aeb aed aee aeg aei aer aex ag- aga agb agd age agg agi agr agx ai- aia aib aid aie aig aii air aix ar- ara arb ard are arg ari arr arx ax- axa axe axi axr axx baa bab bad bae bag bai bar bax bba bbb bbd bbe bbg bbi bbr bbx bda bdb bdd bde bdg bdi bdr bdx be- bea beb bed bee beg bei ber bex bga bgb bgd bge bgg bgi bgr bgx bi- bia bib bid bie big bii bir bix bra brb brd bre brg bri brr brx bxb bxd bxi bxx daa dab dad dae dag dai dar dax dba dbb dbd dbe dbg dbi dbr dbx dda ddb ddd dde ddg ddi ddr ddx de- dea deb ded dee deg dei der dex dga dgd dge dgg dgi dgr di- dia dib did die dig dii dir dix dra drb drd dre drg dri drr drx dxd dxi dxr dxx eaa eab ead eae eag eai ear eax eba ebb ebd ebe ebg ebi ebr ebx ed- eda edb edd ede edg edi edr edx eea eeb eed eee eeg eer eex ega egb egd ege egg egi egr egx eia eib eid eie eig eii eir eix era erb erd ere erg eri err ex- exa exd exe exi exr exx g-d gaa gab gad gae gag gai gar gba gbd gbe gbg gbi gbr gbx gda gdb gdd gde gdi gdr gdx ge- gea geb ged gee geg gei ger gex gga ggb ggd ggg ggi ggr gia gib gid gie gig gii gir gra grb grd gre grg gri grr grx gxa i-d ia- iaa iab iad iae iag iai iar iba ibb ibd ibe ibg ibi ibr ibx ida idb idd ide idg idi idr idx ie- iea ied iee ieg iei ier iex iga igb igd ige igg igi igr iia iib iid iie iii iir iix ir- ira irb ird ire irg iri irr irx ixe ixi ra- raa rab rad rae rag rai rar rax rba rbb rbd rbe rbg rbi rbr rbx rda rdb rdd rde rdg rdi rdr rdx re- rea reb red ree reg rei rer rex rga rgb rgd rge rgg rgi rgr rgx ria rib rid rie rig rii rir rix rra rrb rrd rrg rri rrr rxr xaa xad xag xar xbe xbr xbx xda xdb xde xdi xdr xed xee xeg xer xex xge xgi xia xie xii xix xrd xrx xxi xxx