a-a a-b aaa aab aag aak aar ab- aba abb abg abk abr ag- aga agb agg agk agr aka akb akg akk akr ar- ara arb arg ark arr baa bab bag bak bar bba bbb bbg bbk bbr bga bgb bgg bgk bgr bka bkb bkg bkk bkr bra brb brg brk brr gaa gab gag gak gar gba gbg gbk gbr gga ggb ggg ggr gka gkb gra grb grg grk grr ka- kaa kab kag kak kar kba kbb kbk kbr kga kgb kkb kkk kkr kra krg krk krr ra- raa rab rag rak rar rba rbb rbg rbk rbr rga rgb rgg rgk rgr rkb rkg rkk rra rrb rrg rrk rrr