a-a a-b a-c a-z aaa aab aac aao aar aau aaz ab- aba abb abc abo abr abu abz ac- aca acb acc aco acr acu acz aoa aob aoc aoo aor aou ar- ara arb arc aro arr aru arz au- aua aub auc auo aur auz az- aza azb azo azu azz b-u baa bab bac bao bar bau baz bba bbb bbc bbo bbr bbu bca bcb bcc bco bcr bcu bcz boa bob boc boo bor bou boz bra brb bro brr bru brz bua bub buc buo bur buu buz bza bzo bzr bzu bzz c-- caa cab cac cao car cau caz cba cbb cbc cbo cbr cbu cbz cca ccb ccc cco ccr ccu ccz co- coa cob coc coo cor cou coz cra crb crc cro crr cru crz cua cub cuc cuo cur cuu cuz cz- czc czo oaa oab oac oao oar oau ob- oba obb obc obo obr obu oc- oca ocb occ oco ocr ocu ocz oo- ooa oob ooc ooo oor or- ora orb orc oro orr oru orz ou- oua ouc ouo our oza ozo ozu ozz ra- raa rab rac rao rar rau raz rba rbb rbc rbo rbr rbu rca rcb rcc rco rcr rcu roa rob roc roo ror rou roz rra rrb rrc rrr rru rua rub ruc ruo rur ruu ruz rza rzb rzo ua- uaa uab uac uao uar uau uaz uba ubb ubc ubo ubr ubu uca ucb ucc uco ucr ucu uoa uob uoc uoo uor ur- ura urb urc uro urr uru urz uua uuc uur uuu uza uzb uzo uzu zaa zab zac zao zar zaz zbb zbc zbr zco zo- zoa zob zoc zoo zor zou zro zub zuc zur zuz zzr zzz