a-a a-b a-z aaa aab aao aar aay aaz ab- aba abb abo abr aby abz aoa aob aoo aor ar- ara arb aro arr ary arz ay- aya ayo ayr ayz az- aza azb azo azy azz baa bab bao bar bay baz bba bbb bbo bbr bby boa bob boo bor boy boz bra brb bro brr bry brz by- bya byo byr byz bza bzo bzr bzz oaa oab oao oar ob- oba obb obo obr oby oo- ooa oob ooo oor or- ora orb oro orr ory orz oya oyo oza ozo ozz ra- raa rab rao rar ray raz rba rbb rbo rbr roa rob roo ror roy roz rra rrb rrr ry- rya ryo ryr ryy ryz rza rzb rzo rzy yaa yab yao yar yay yaz ybr yby ybz yob yoo yor yoy yra yro yyb yyy yyz yzb yzr yzy zaa zab zao zar zay zaz zbb zbr zby zo- zoa zob zoo zor zro zzr zzy zzz