a-a a-b aaa aab aao aap aay ab- aba abb abo abp aby aoa aob aoo aop ap- apa apb apo app apy ay- aya ayo ayp b-p baa bab bao bap bay bba bbb bbo bbp bby boa bob boo bop boy bpa bpb bpo bpp bpy by- bya byo byp oaa oab oao oap ob- oba obb obo obp oby oo- ooa oob ooo oop op- opa opb opo opp opy oya oyo p-p paa pab pao pap pay pba pbb pbo pbp pby poa pob poo pop poy ppa ppb ppo ppp py- pya pyb pyo yaa yab yao yap yay ybp yby yob yoo yop yoy ypa ypo yyb yyy