a-a a-t aaa aaf aan aat aax af- afa aff afn aft afx an- ana anf ann ant anx at- ata atf atn att atx ax- axa axn axt axx faa faf fan fat fax ffa fff ffn fft ffx fna fnf fnn fnt fnx fta ftf ftn ftt ftx fxt fxx naa naf nan nat nax nfa nff nfn nft nna nnf nnn nnt nta ntf ntn ntt ntx nxt t-x taa taf tan tat tax tfa tff tfn tft tfx tna tnf tnn tnt tnx tta ttf ttn ttt ttx txf txn txt xaa xaf xan xat xfa xfn xft xfx xna xtf xtx xxx