a-a a-b a-c aaa aab aac aad aak aan aao ab- aba abb abc abd abk abn abo ac- aca acb acc acd ack acn aco ad- ada adb adc add adk adn ado aka akb akc akd akk akn ako an- ana anb anc and ank ann ano aoa aob aoc aod aok aon aoo baa bab bac bad bak ban bao bba bbb bbc bbd bbk bbn bbo bca bcb bcc bcd bck bcn bco bda bdb bdc bdd bdk bdo bka bkb bkc bkk bkn bko bna bnb bnc bnd bnk bnn bno boa bob boc bod bok bon boo c-- caa cab cac cad cak can cao cba cbb cbc cbd cbk cbn cbo cca ccb ccc ccd cck ccn cco cda cdb cdc cdd cdk cdn cdo cka ckb ckc ckd cko cn- cna cnb cnc cnd cnn cno co- coa cob coc cod cok con coo daa dab dac dad dak dan dao dba dbb dbc dbd dbk dbn dbo dca dcb dcc dcd dck dcn dco dda ddb ddc ddd ddk ddn ddo dka dkb dkc dkk dko dna dnb dnc dnd dnk dnn dno doa dob doc dod dok don doo ka- kaa kab kac kad kak kan kao kba kbb kbc kbd kbk kbn kbo kca kcb kcc kcd kck kcn kda kdb kdc kdk kdo kkb kkc kkk kkn kn- kna knc knd knk knn kno koa kob koc kod kok kon koo naa nab nac nad nak nan nao nba nbb nbc nbd nbk nbn nbo nca ncb ncc ncd nck ncn nco nda ndb ndc ndd ndk ndn ndo nka nkc nkk nkn nko nna nnb nnc nnk nnn nno no- noa nob noc nod nok non noo oaa oab oac oad oak oan oao ob- oba obb obc obd obk obn obo oc- oca ocb occ ocd ock ocn oco oda odb odc odd odn odo oka okb okc okd okk oko on- ona onb onc ond onk onn ono oo- ooa oob ooc ood ook oon ooo