a-a a-b aaa aab aae aag aan ab- aba abb abe abg abn aea aeb aee aeg aen ag- aga agb age agg agn an- ana anb ane ang ann baa bab bae bag ban bba bbb bbe bbg bbn be- bea beb bee beg ben bga bgb bge bgg bgn bna bnb bne bng bnn eaa eab eae eag ean eba ebb ebe ebg ebn eea eeb eee eeg een ega egb ege egg egn en- ena enb ene eng enn gaa gab gae gag gan gba gbe gbg gbn ge- gea geb gee geg gen gga ggb ggg ggn gna gnb gne gnn naa nab nae nag nan nba nbb nbe nbg nbn ne- nea neb nee neg nen nga ngb nge ngg ngn nna nnb nne nng nnn