a-a a-b a-t aaa aab aao aap aas aat ab- aba abb abo abp abs abt aoa aob aoo aop aos aot ap- apa apb apo app aps apt as- asa asb aso asp ass ast at- ata atb ato atp ats att b-p baa bab bao bap bas bat bba bbb bbo bbp bbs bbt boa bob boo bop bos bot bpa bpb bpo bpp bps bpt bsa bsb bso bsp bss bst bta btb bto btp bts btt oaa oab oao oap oas oat ob- oba obb obo obp obs obt oo- ooa oob ooo oop oos oot op- opa opb opo opp ops opt os- osa osb oso osp oss ost ot- ota otb oto otp ots ott p-p paa pab pao pap pas pat pba pbb pbo pbp pbs pbt poa pob poo pop pos pot ppa ppb ppo ppp pps ppt ps- psa psb pso psp pss pst pt- pta ptb pto ptp pts ptt saa sab sao sap sas sat sba sbb sbo sbp sbs sbt soa sob soo sop sos sot spa spb spo spp sps spt ss- ssa ssb sso ssp sss sst sta stb sto stp sts stt taa tab tao tap tas tat tba tbb tbo tbp tbs tbt to- toa tob too top tos tot tpa tpb tpo tpp tps tpt tsa tsb tso tsp tss tst tta ttb tto ttp tts ttt