a-a a-b aaa aab aag aan aar ab- aba abb abg abn abr ag- aga agb agg agn agr an- ana anb ang ann anr ar- ara arb arg arn arr baa bab bag ban bar bba bbb bbg bbn bbr bga bgb bgg bgn bgr bna bnb bng bnn bnr bra brb brg brn brr gaa gab gag gan gar gba gbg gbn gbr gga ggb ggg ggn ggr gna gnb gnn gnr gra grb grg grn grr naa nab nag nan nar nba nbb nbg nbn nbr nga ngb ngg ngn nna nnb nng nnn nra nrb nrg nrn nrr ra- raa rab rag ran rar rba rbb rbg rbn rbr rga rgb rgg rgn rgr rna rnb rng rnn rnr rra rrb rrg rrn rrr