a-a a-b a-z aaa aab aan aao aaz ab- aba abb abn abo abz an- ana anb ann ano anz aoa aob aon aoo az- aza azb azn azo azz baa bab ban bao baz bba bbb bbn bbo bna bnb bnn bno bnz boa bob bon boo boz bza bzn bzo bzz naa nab nan nao naz nba nbb nbn nbo nna nnb nnn nno nnz no- noa nob non noo noz nzb nzo nzz oaa oab oan oao ob- oba obb obn obo on- ona onb onn ono oo- ooa oob oon ooo oza ozo ozz zaa zab zan zao zaz zbb znn zno zo- zoa zob zon zoo zzz