a-a a-b a-c aaa aab aac aag aan ab- aba abb abc abg abn ac- aca acb acc acg acn ag- aga agb agc agg agn an- ana anb anc ang ann baa bab bac bag ban bba bbb bbc bbg bbn bca bcb bcc bcg bcn bga bgb bgc bgg bgn bna bnb bnc bng bnn c-- caa cab cac cag can cba cbb cbc cbg cbn cca ccb ccc ccg ccn cga cgb cgc cgg cgn cn- cna cnb cnc cng cnn gaa gab gac gag gan gba gbc gbg gbn gca gcb gcc gcg gcn gga ggb ggc ggg ggn gna gnb gnc gnn naa nab nac nag nan nba nbb nbc nbg nbn nca ncb ncc ncg ncn nga ngb ngc ngg ngn nna nnb nnc nng nnn