a-a a-b a-z aaa aab aar aas aaz ab- aba abb abr abs abz ar- ara arb arr ars arz as- asa asb asr ass asz az- aza azb azs azz baa bab bar bas baz bba bbb bbr bbs bra brb brr brs brz bsa bsb bsr bss bza bzr bzs bzz ra- raa rab rar ras raz rba rbb rbr rbs rra rrb rrr rrs rsa rsb rsr rss rza rzb saa sab sar sas saz sba sbb sbr sbs sr- sra srb srr srs ss- ssa ssb ssr sss ssz sza szr zaa zab zar zas zaz zbb zbr zbs zrs zsa zsz zzr zzs zzz