a-a a-b a-t aaa aab aag aar aat ab- aba abb abg abr abt ag- aga agb agg agr agt ar- ara arb arg arr art at- ata atb atg atr att baa bab bag bar bat bba bbb bbg bbr bbt bga bgb bgg bgr bgt bra brb brg brr brt bta btb btg btr btt gaa gab gag gar gat gba gbg gbr gbt gga ggb ggg ggr ggt gra grb grg grr grt gta gtb gtg gtr gtt ra- raa rab rag rar rat rba rbb rbg rbr rbt rga rgb rgg rgr rgt rra rrb rrg rrr rrt rta rtb rtg rtr rtt taa tab tag tar tat tba tbb tbg tbr tbt tga tgb tgg tgr tgt tra trb trg trr trt tta ttb ttg ttr ttt