a-a a-b a-c aaa aab aac aah aan aao ab- aba abb abc abh abn abo ac- aca acb acc ach acn aco aha ahb ahc ahh ahn aho an- ana anb anc anh ann ano aoa aob aoc aoh aon aoo baa bab bac bah ban bao bba bbb bbc bbh bbn bbo bca bcb bcc bch bcn bco bha bhb bhc bhh bho bna bnb bnc bnn bno boa bob boc boh bon boo c-- caa cab cac cah can cao cba cbb cbc cbh cbn cbo cca ccb ccc cch ccn cco ch- cha chb chc chh chn cho cn- cna cnb cnc cnh cnn cno co- coa cob coc coh con coo haa hab hac hah han hao hba hbb hbc hbh hbn hbo hca hcb hcc hch hcn hco hha hhb hhc hhh hhn hho hna hnb hnc hnh hnn hno hoa hob hoc hoh hon hoo naa nab nac nah nan nao nba nbb nbc nbn nbo nca ncb ncc nch ncn nco nha nhb nhc nhh nhn nna nnb nnc nnh nnn nno no- noa nob noc noh non noo oaa oab oac oah oan oao ob- oba obb obc obh obn obo oc- oca ocb occ och ocn oco oha ohc ohh ohn oho on- ona onb onc onh onn ono oo- ooa oob ooc ooh oon ooo