a-a a-b aaa aab aad aao aap ab- aba abb abd abo abp ad- ada adb add ado adp aoa aob aod aoo aop ap- apa apb apd apo app b-p baa bab bad bao bap bba bbb bbd bbo bbp bda bdb bdd bdo bdp boa bob bod boo bop bpa bpb bpd bpo bpp daa dab dad dao dap dba dbb dbd dbo dbp dda ddb ddd ddo ddp doa dob dod doo dop dpa dpb dpd dpo dpp oaa oab oad oao oap ob- oba obb obd obo obp oda odb odd odo odp oo- ooa oob ood ooo oop op- opa opb opd opo opp p-p paa pab pad pao pap pba pbb pbd pbo pbp pda pdb pdd pdo pdp poa pob pod poo pop ppa ppb ppd ppo ppp