a-a a-b aaa aab aae aag aak aan ab- aba abb abe abg abk abn aea aeb aee aeg aek aen ag- aga agb age agg agk agn aka akb ake akg akk akn an- ana anb ane ang ank ann baa bab bae bag bak ban bba bbb bbe bbg bbk bbn be- bea beb bee beg bek ben bga bgb bge bgg bgk bgn bka bkb bke bkg bkk bkn bna bnb bne bng bnk bnn eaa eab eae eag eak ean eba ebb ebe ebg ebk ebn eea eeb eee eeg eek een ega egb ege egg egn eka ekb eke ekg en- ena enb ene eng enk enn gaa gab gae gag gak gan gba gbe gbg gbk gbn ge- gea geb gee geg gek gen gga ggb ggg ggn gka gkb gkn gna gnb gne gnn ka- kaa kab kae kag kak kan kba kbb kbe kbk kbn ke- kea keb kee keg kek ken kga kgb kkb kke kkk kkn kn- kna kne kng knk knn naa nab nae nag nak nan nba nbb nbe nbg nbk nbn ne- nea neb nee neg nek nen nga ngb nge ngg ngk ngn nka nke nkk nkn nna nnb nne nng nnk nnn