a-a a-b a-c aaa aab aac aad aan aao ab- aba abb abc abd abn abo ac- aca acb acc acd acn aco ad- ada adb adc add adn ado an- ana anb anc and ann ano aoa aob aoc aod aon aoo baa bab bac bad ban bao bba bbb bbc bbd bbn bbo bca bcb bcc bcd bcn bco bda bdb bdc bdd bdo bna bnb bnc bnd bnn bno boa bob boc bod bon boo c-- caa cab cac cad can cao cba cbb cbc cbd cbn cbo cca ccb ccc ccd ccn cco cda cdb cdc cdd cdn cdo cn- cna cnb cnc cnd cnn cno co- coa cob coc cod con coo daa dab dac dad dan dao dba dbb dbc dbd dbn dbo dca dcb dcc dcd dcn dco dda ddb ddc ddd ddn ddo dna dnb dnc dnd dnn dno doa dob doc dod don doo naa nab nac nad nan nao nba nbb nbc nbd nbn nbo nca ncb ncc ncd ncn nco nda ndb ndc ndd ndn ndo nna nnb nnc nnn nno no- noa nob noc nod non noo oaa oab oac oad oan oao ob- oba obb obc obd obn obo oc- oca ocb occ ocd ocn oco oda odb odc odd odn odo on- ona onb onc ond onn ono oo- ooa oob ooc ood oon ooo