-er a-a a-b a-t aaa aab aae aag aar aat aax ab- aba abb abe abg abr abt abx aea aeb aee aeg aer aet aex ag- aga agb age agg agr agt agx ar- ara arb are arg arr art arx at- ata atb ate atg atr att atx ax- axa axe axr axt axx baa bab bae bag bar bat bax bba bbb bbe bbg bbr bbt bbx be- bea beb bee beg ber bet bex bga bgb bge bgg bgr bgt bgx bra brb bre brg brr brt brx bta btb bte btg btr btt btx bxb bxx eaa eab eae eag ear eat eax eba ebb ebe ebg ebr ebt ebx eea eeb eee eeg eer eet eex ega egb ege egg egr egt egx era erb ere erg err ert eta etb ete etg etr ett etx ex- exa exe exr ext exx gaa gab gae gag gar gat gba gbe gbg gbr gbt gbx ge- gea geb gee geg ger get gex gga ggb ggg ggr ggt gra grb gre grg grr grt grx gta gtb gte gtg gtr gtt gtx gxa gxt ra- raa rab rae rag rar rat rax rba rbb rbe rbg rbr rbt rbx re- rea reb ree reg rer ret rex rga rgb rge rgg rgr rgt rgx rra rrb rrg rrr rrt rta rtb rte rtg rtr rtt rtx rxr t-x taa tab tae tag tar tat tax tba tbb tbe tbg tbr tbt te- tea teb tee teg ter tet tex tga tgb tge tgg tgr tgt tra trb tre trg trr trt trx tta ttb tte ttg ttr ttt ttx txe txt xaa xag xar xat xbe xbr xbx xee xeg xer xet xex xge xrt xrx xtr xtx xxx