a-a a-b a-z aaa aab aar aau aaz ab- aba abb abr abu abz ar- ara arb arr aru arz au- aua aub aur auz az- aza azb azu azz b-u baa bab bar bau baz bba bbb bbr bbu bra brb brr bru brz bua bub bur buu buz bza bzr bzu bzz ra- raa rab rar rau raz rba rbb rbr rbu rra rrb rrr rru rua rub rur ruu ruz rza rzb ua- uaa uab uar uau uaz uba ubb ubr ubu ur- ura urb urr uru urz uua uur uuu uza uzb uzu zaa zab zar zaz zbb zbr zub zur zuz zzr zzz