a-a a-b a-t aaa aab aap aas aat ab- aba abb abp abs abt ap- apa apb app aps apt as- asa asb asp ass ast at- ata atb atp ats att b-p baa bab bap bas bat bba bbb bbp bbs bbt bpa bpb bpp bps bpt bsa bsb bsp bss bst bta btb btp bts btt p-p paa pab pap pas pat pba pbb pbp pbs pbt ppa ppb ppp pps ppt ps- psa psb psp pss pst pt- pta ptb ptp pts ptt saa sab sap sas sat sba sbb sbp sbs sbt spa spb spp sps spt ss- ssa ssb ssp sss sst sta stb stp sts stt taa tab tap tas tat tba tbb tbp tbs tbt tpa tpb tpp tps tpt tsa tsb tsp tss tst tta ttb ttp tts ttt