a-a a-b aaa aab aak aao aap aay ab- aba abb abk abo abp aby aka akb akk ako akp aoa aob aok aoo aop ap- apa apb apk apo app apy ay- aya ayk ayo ayp b-p baa bab bak bao bap bay bba bbb bbk bbo bbp bby bka bkb bkk bko bkp boa bob bok boo bop boy bpa bpb bpo bpp bpy by- bya byk byo byp ka- kaa kab kak kao kap kay kba kbb kbk kbo kbp kkb kkk kkp kky koa kob kok koo kop koy kpa kpk kpo kpp kya kyo kyp oaa oab oak oao oap ob- oba obb obk obo obp oby oka okb okk oko okp oo- ooa oob ook ooo oop op- opa opb opk opo opp opy oya oyo p-p paa pab pak pao pap pay pba pbb pbk pbo pbp pby pka pkb pko pkp pky poa pob pok poo pop poy ppa ppb ppk ppo ppp py- pya pyb pyk pyo yaa yab yak yao yap yay ybp yby yka ykk yob yok yoo yop yoy ypa ypo yyb yyy