a-a a-b aaa aab aag aar aas ab- aba abb abg abr abs ag- aga agb agg agr ags ar- ara arb arg arr ars as- asa asb asg asr ass baa bab bag bar bas bba bbb bbg bbr bbs bga bgb bgg bgr bgs bra brb brg brr brs bsa bsb bsg bsr bss gaa gab gag gar gas gba gbg gbr gbs gga ggb ggg ggr ggs gra grb grg grr grs gsa gsb gsg gsr gss ra- raa rab rag rar ras rba rbb rbg rbr rbs rga rgb rgg rgr rgs rra rrb rrg rrr rrs rsa rsb rsg rsr rss saa sab sag sar sas sba sbb sbg sbr sbs sga sgb sgg sgr sgs sr- sra srb srg srr srs ss- ssa ssb ssg ssr sss