-er a-a a-b a-t aaa aab aae aag aar aas aat ab- aba abb abe abg abr abs abt aea aeb aee aeg aer aes aet ag- aga agb age agg agr ags agt ar- ara arb are arg arr ars art as- asa asb ase asg asr ass ast at- ata atb ate atg atr ats att baa bab bae bag bar bas bat bba bbb bbe bbg bbr bbs bbt be- bea beb bee beg ber bes bet bga bgb bge bgg bgr bgs bgt bra brb bre brg brr brs brt bsa bsb bse bsg bsr bss bst bta btb bte btg btr bts btt eaa eab eae eag ear eas eat eba ebb ebe ebg ebr ebs ebt eea eeb eee eeg eer ees eet ega egb ege egg egr egs egt era erb ere erg err ers ert es- esa esb ese esg esr ess est eta etb ete etg etr ets ett gaa gab gae gag gar gas gat gba gbe gbg gbr gbs gbt ge- gea geb gee geg ger ges get gga ggb ggg ggr ggs ggt gra grb gre grg grr grs grt gsa gsb gse gsg gsr gss gst gta gtb gte gtg gtr gts gtt ra- raa rab rae rag rar ras rat rba rbb rbe rbg rbr rbs rbt re- rea reb ree reg rer res ret rga rgb rge rgg rgr rgs rgt rra rrb rrg rrr rrs rrt rsa rsb rse rsg rsr rss rst rta rtb rte rtg rtr rts rtt saa sab sae sag sar sas sat sba sbb sbe sbg sbr sbs sbt se- sea seb see seg ser ses set sga sgb sge sgg sgr sgs sgt sr- sra srb sre srg srr srs srt ss- ssa ssb sse ssg ssr sss sst sta stb ste stg str sts stt taa tab tae tag tar tas tat tba tbb tbe tbg tbr tbs tbt te- tea teb tee teg ter tes tet tga tgb tge tgg tgr tgs tgt tra trb tre trg trr trs trt tsa tsb tse tsg tsr tss tst tta ttb tte ttg ttr tts ttt