a-a a-b a-t aaa aab aao aap aat ab- aba abb abo abp abt aoa aob aoo aop aot ap- apa apb apo app apt at- ata atb ato atp att b-p baa bab bao bap bat bba bbb bbo bbp bbt boa bob boo bop bot bpa bpb bpo bpp bpt bta btb bto btp btt oaa oab oao oap oat ob- oba obb obo obp obt oo- ooa oob ooo oop oot op- opa opb opo opp opt ot- ota otb oto otp ott p-p paa pab pao pap pat pba pbb pbo pbp pbt poa pob poo pop pot ppa ppb ppo ppp ppt pt- pta ptb pto ptp ptt taa tab tao tap tat tba tbb tbo tbp tbt to- toa tob too top tot tpa tpb tpo tpp tpt tta ttb tto ttp ttt