a-a a-b a-c a-z aaa aab aac aak aao aas aaz ab- aba abb abc abk abo abs abz ac- aca acb acc ack aco acs acz aka akb akc akk ako aks aoa aob aoc aok aoo aos as- asa asb asc ask aso ass asz az- aza azb azo azs azz baa bab bac bak bao bas baz bba bbb bbc bbk bbo bbs bca bcb bcc bck bco bcs bcz bka bkb bkc bkk bko bks boa bob boc bok boo bos boz bsa bsb bsc bsk bso bss bza bzo bzs bzz c-- caa cab cac cak cao cas caz cba cbb cbc cbk cbo cbs cbz cca ccb ccc cck cco ccs ccz cka ckb ckc cko cks co- coa cob coc cok coo cos coz csa csb csc csk cso css csz cz- czc czk czo k-z ka- kaa kab kac kak kao kas kaz kba kbb kbc kbk kbo kbs kbz kca kcb kcc kck kcs kkb kkc kkk kks koa kob koc kok koo kos koz ksa ksb ksc ksk kso kss kzo oaa oab oac oak oao oas ob- oba obb obc obk obo obs oc- oca ocb occ ock oco ocs ocz oka okb okc okk oko oks oo- ooa oob ooc ook ooo oos os- osa osb osc osk oso oss oza ozo ozs ozz saa sab sac sak sao sas saz sba sbb sbc sbk sbo sbs sca scb scc sck sco scs sk- ska skb skc skk sko sks soa sob soc sok soo sos soz ss- ssa ssb ssc ssk sso sss ssz sza zaa zab zac zak zao zas zaz zbb zbc zbs zco zcs zka zks zo- zoa zob zoc zok zoo zos zsa zsz zzs zzz