a-a a-b a-c a-z aaa aab aac aar aau aaz ab- aba abb abc abr abu abz ac- aca acb acc acr acu acz ar- ara arb arc arr aru arz au- aua aub auc aur auz az- aza azb azu azz b-u baa bab bac bar bau baz bba bbb bbc bbr bbu bca bcb bcc bcr bcu bcz bra brb brr bru brz bua bub buc bur buu buz bza bzr bzu bzz c-- caa cab cac car cau caz cba cbb cbc cbr cbu cbz cca ccb ccc ccr ccu ccz cra crb crc crr cru crz cua cub cuc cur cuu cuz cz- czc ra- raa rab rac rar rau raz rba rbb rbc rbr rbu rca rcb rcc rcr rcu rra rrb rrc rrr rru rua rub ruc rur ruu ruz rza rzb ua- uaa uab uac uar uau uaz uba ubb ubc ubr ubu uca ucb ucc ucr ucu ur- ura urb urc urr uru urz uua uuc uur uuu uza uzb uzu zaa zab zac zar zaz zbb zbc zbr zub zuc zur zuz zzr zzz