a-a a-b a-c aaa aab aac aae aak aan aao ab- aba abb abc abe abk abn abo ac- aca acb acc ace ack acn aco aea aeb aec aee aek aen aeo aka akb akc ake akk akn ako an- ana anb anc ane ank ann ano aoa aob aoc aoe aok aon aoo baa bab bac bae bak ban bao bba bbb bbc bbe bbk bbn bbo bca bcb bcc bce bck bcn bco be- bea beb bec bee bek ben beo bka bkb bkc bke bkk bkn bko bna bnb bnc bne bnk bnn bno boa bob boc boe bok bon boo c-- caa cab cac cae cak can cao cba cbb cbc cbe cbk cbn cbo cca ccb ccc cce cck ccn cco ce- cea ceb cec cee cek cen ceo cka ckb ckc cko cn- cna cnb cnc cne cnn cno co- coa cob coc coe cok con coo eaa eab eac eae eak ean eao eba ebb ebc ebe ebk ebn ebo ec- eca ecb ecc ece eck ecn eco eea eeb eec eee eek een eeo eka ekb ekc eke eko en- ena enb enc ene enk enn eno eo- eoa eob eoc eoe eok eon eoo ka- kaa kab kac kae kak kan kao kba kbb kbc kbe kbk kbn kbo kca kcb kcc kce kck kcn ke- kea keb kec kee kek ken keo kkb kkc kke kkk kkn kn- kna knc kne knk knn kno koa kob koc koe kok kon koo naa nab nac nae nak nan nao nba nbb nbc nbe nbk nbn nbo nca ncb ncc nce nck ncn nco ne- nea neb nec nee nek nen neo nka nkc nke nkk nkn nko nna nnb nnc nne nnk nnn nno no- noa nob noc noe nok non noo oaa oab oac oae oak oan oao ob- oba obb obc obe obk obn obo oc- oca ocb occ ock ocn oco oea oeb oec oee oen oeo oka okb okc oke okk oko on- ona onb onc one onk onn ono oo- ooa oob ooc ook oon ooo