a-a a-b aaa aab aak aao aap ab- aba abb abk abo abp aka akb akk ako akp aoa aob aok aoo aop ap- apa apb apk apo app b-p baa bab bak bao bap bba bbb bbk bbo bbp bka bkb bkk bko bkp boa bob bok boo bop bpa bpb bpo bpp ka- kaa kab kak kao kap kba kbb kbk kbo kbp kkb kkk kkp koa kob kok koo kop kpa kpk kpo kpp oaa oab oak oao oap ob- oba obb obk obo obp oka okb okk oko okp oo- ooa oob ook ooo oop op- opa opb opk opo opp p-p paa pab pak pao pap pba pbb pbk pbo pbp pka pkb pko pkp poa pob pok poo pop ppa ppb ppk ppo ppp