a-a a-b a-z aaa aab aao aau aaz ab- aba abb abo abu abz aoa aob aoo aou au- aua aub auo auz az- aza azb azo azu azz b-u baa bab bao bau baz bba bbb bbo bbu boa bob boo bou boz bua bub buo buu buz bza bzo bzu bzz oaa oab oao oau ob- oba obb obo obu oo- ooa oob ooo ou- oua ouo oza ozo ozu ozz ua- uaa uab uao uau uaz uba ubb ubo ubu uoa uob uoo uua uuu uza uzb uzo uzu zaa zab zao zaz zbb zo- zoa zob zoo zou zub zuz zzz