a-a a-b a-c aaa aab aac aak aao aau ab- aba abb abc abk abo abu ac- aca acb acc ack aco acu aka akb akc akk ako aku aoa aob aoc aok aoo aou au- aua aub auc auk auo b-u baa bab bac bak bao bau bba bbb bbc bbk bbo bbu bca bcb bcc bck bco bcu bka bkb bkc bkk bko boa bob boc bok boo bou bua bub buc buk buo buu c-- caa cab cac cak cao cau cba cbb cbc cbk cbo cbu cca ccb ccc cck cco ccu cka ckb ckc cko co- coa cob coc cok coo cou cua cub cuc cuk cuo cuu ka- kaa kab kac kak kao kau kba kbb kbc kbk kbo kbu kca kcb kcc kck kcu kkb kkc kkk kku koa kob koc kok koo kou kub kuc kuk kuu oaa oab oac oak oao oau ob- oba obb obc obk obo obu oc- oca ocb occ ock oco ocu oka okb okc okk oko oku oo- ooa oob ooc ook ooo ou- oua ouc ouk ouo ua- uaa uab uac uak uao uau uba ubb ubc ubk ubo ubu uca ucb ucc uck uco ucu uka ukb ukc ukk uku uoa uob uoc uok uoo uua uuc uuu