a-a a-b a-t aaa aab aad aas aat ab- aba abb abd abs abt ad- ada adb add ads adt as- asa asb asd ass ast at- ata atb atd ats att baa bab bad bas bat bba bbb bbd bbs bbt bda bdb bdd bds bdt bsa bsb bsd bss bst bta btb btd bts btt daa dab dad das dat dba dbb dbd dbs dbt dda ddb ddd dds ddt dsa dsb dsd dss dst dta dtb dtd dts dtt saa sab sad sas sat sba sbb sbd sbs sbt sda sdb sdd sds sdt ss- ssa ssb ssd sss sst sta stb std sts stt taa tab tad tas tat tba tbb tbd tbs tbt tda tdb tdd tds tdt tsa tsb tsd tss tst tta ttb ttd tts ttt