a-a a-b a-z aaa aab aak aao aar aaz ab- aba abb abk abo abr abz aka akb akk ako akr aoa aob aok aoo aor ar- ara arb ark aro arr arz az- aza azb azo azz baa bab bak bao bar baz bba bbb bbk bbo bbr bka bkb bkk bko bkr boa bob bok boo bor boz bra brb brk bro brr brz bza bzo bzr bzz k-z ka- kaa kab kak kao kar kaz kba kbb kbk kbo kbr kbz kkb kkk kkr koa kob kok koo kor koz kra krk kro krr kzo oaa oab oak oao oar ob- oba obb obk obo obr oka okb okk oko okr oo- ooa oob ook ooo oor or- ora orb ork oro orr orz oza ozo ozz ra- raa rab rak rao rar raz rba rbb rbk rbo rbr rkb rkk rko rkz roa rob rok roo ror roz rra rrb rrk rrr rza rzb rzo zaa zab zak zao zar zaz zbb zbr zka zo- zoa zob zok zoo zor zro zzr zzz