a-a a-b a-z aaa aab aao aar aau aaz ab- aba abb abo abr abu abz aoa aob aoo aor aou ar- ara arb aro arr aru arz au- aua aub auo aur auz az- aza azb azo azu azz b-u baa bab bao bar bau baz bba bbb bbo bbr bbu boa bob boo bor bou boz bra brb bro brr bru brz bua bub buo bur buu buz bza bzo bzr bzu bzz oaa oab oao oar oau ob- oba obb obo obr obu oo- ooa oob ooo oor or- ora orb oro orr oru orz ou- oua ouo our oza ozo ozu ozz ra- raa rab rao rar rau raz rba rbb rbo rbr rbu roa rob roo ror rou roz rra rrb rrr rru rua rub ruo rur ruu ruz rza rzb rzo ua- uaa uab uao uar uau uaz uba ubb ubo ubr ubu uoa uob uoo uor ur- ura urb uro urr uru urz uua uur uuu uza uzb uzo uzu zaa zab zao zar zaz zbb zbr zo- zoa zob zoo zor zou zro zub zur zuz zzr zzz