a-a a-b a-c a-z aaa aab aac aan aao aaz ab- aba abb abc abn abo abz ac- aca acb acc acn aco acz an- ana anb anc ann ano anz aoa aob aoc aon aoo az- aza azb azn azo azz baa bab bac ban bao baz bba bbb bbc bbn bbo bca bcb bcc bcn bco bcz bna bnb bnc bnn bno bnz boa bob boc bon boo boz bza bzn bzo bzz c-- caa cab cac can cao caz cba cbb cbc cbn cbo cbz cca ccb ccc ccn cco ccz cn- cna cnb cnc cnn cno co- coa cob coc con coo coz cz- czc czo naa nab nac nan nao naz nba nbb nbc nbn nbo nca ncb ncc ncn nco nna nnb nnc nnn nno nnz no- noa nob noc non noo noz nzb nzo nzz oaa oab oac oan oao ob- oba obb obc obn obo oc- oca ocb occ ocn oco ocz on- ona onb onc onn ono oo- ooa oob ooc oon ooo oza ozo ozz zaa zab zac zan zao zaz zbb zbc zco znc znn zno zo- zoa zob zoc zon zoo zzz