a-a a-t aaa aaf aas aat aax af- afa aff afs aft afx as- asa asf ass ast asx at- ata atf ats att atx ax- axa axs axt axx faa faf fas fat fax ffa fff ffs fft ffx fsa fsf fss fst fsx fta ftf fts ftt ftx fxs fxt fxx saa saf sas sat sax sfa sff sfs sft sfx ss- ssa ssf sss sst ssx sta stf sts stt stx sxs sxt t-x taa taf tas tat tax tfa tff tfs tft tfx tsa tsf tss tst tsx tta ttf tts ttt ttx txf txs txt xaa xaf xas xat xfa xfs xft xfx xsa xss xst xtf xts xtx xxx