a-a a-b aaa aab aak aao aau ab- aba abb abk abo abu aka akb akk ako aku aoa aob aok aoo aou au- aua aub auk auo b-u baa bab bak bao bau bba bbb bbk bbo bbu bka bkb bkk bko boa bob bok boo bou bua bub buk buo buu ka- kaa kab kak kao kau kba kbb kbk kbo kbu kkb kkk kku koa kob kok koo kou kub kuk kuu oaa oab oak oao oau ob- oba obb obk obo obu oka okb okk oko oku oo- ooa oob ook ooo ou- oua ouk ouo ua- uaa uab uak uao uau uba ubb ubk ubo ubu uka ukb ukk uku uoa uob uok uoo uua uuu