a-a a-b a-z aaa aab aan aar aaz ab- aba abb abn abr abz an- ana anb ann anr anz ar- ara arb arn arr arz az- aza azb azn azz baa bab ban bar baz bba bbb bbn bbr bna bnb bnn bnr bnz bra brb brn brr brz bza bzn bzr bzz naa nab nan nar naz nba nbb nbn nbr nna nnb nnn nnz nra nrb nrn nrr nrz nzb nzz ra- raa rab ran rar raz rba rbb rbn rbr rna rnb rnn rnr rnz rra rrb rrn rrr rza rzb zaa zab zan zar zaz zbb zbr znn zzr zzz