a-a a-b a-z aaa aab aan aao aar aaz ab- aba abb abn abo abr abz an- ana anb ann ano anr anz aoa aob aon aoo aor ar- ara arb arn aro arr arz az- aza azb azn azo azz baa bab ban bao bar baz bba bbb bbn bbo bbr bna bnb bnn bno bnr bnz boa bob bon boo bor boz bra brb brn bro brr brz bza bzn bzo bzr bzz naa nab nan nao nar naz nba nbb nbn nbo nbr nna nnb nnn nno nnz no- noa nob non noo nor noz nra nrb nrn nro nrr nrz nzb nzo nzz oaa oab oan oao oar ob- oba obb obn obo obr on- ona onb onn ono onr oo- ooa oob oon ooo oor or- ora orb orn oro orr orz oza ozo ozz ra- raa rab ran rao rar raz rba rbb rbn rbo rbr rna rnb rnn rno rnr rnz roa rob ron roo ror roz rra rrb rrn rrr rza rzb rzo zaa zab zan zao zar zaz zbb zbr znn zno zo- zoa zob zon zoo zor zro zzr zzz