a-a a-b a-c a-z aaa aab aac aak aao aaz ab- aba abb abc abk abo abz ac- aca acb acc ack aco acz aka akb akc akk ako aoa aob aoc aok aoo az- aza azb azo azz baa bab bac bak bao baz bba bbb bbc bbk bbo bca bcb bcc bck bco bcz bka bkb bkc bkk bko boa bob boc bok boo boz bza bzo bzz c-- caa cab cac cak cao caz cba cbb cbc cbk cbo cbz cca ccb ccc cck cco ccz cka ckb ckc cko co- coa cob coc cok coo coz cz- czc czk czo k-z ka- kaa kab kac kak kao kaz kba kbb kbc kbk kbo kbz kca kcb kcc kck kkb kkc kkk koa kob koc kok koo koz kzo oaa oab oac oak oao ob- oba obb obc obk obo oc- oca ocb occ ock oco ocz oka okb okc okk oko oo- ooa oob ooc ook ooo oza ozo ozz zaa zab zac zak zao zaz zbb zbc zco zka zo- zoa zob zoc zok zoo zzz