a-a a-b aaa aab aae aak aan aao ab- aba abb abe abk abn abo aea aeb aee aek aen aeo aka akb ake akk akn ako an- ana anb ane ank ann ano aoa aob aoe aok aon aoo baa bab bae bak ban bao bba bbb bbe bbk bbn bbo be- bea beb bee bek ben beo bka bkb bke bkk bkn bko bna bnb bne bnk bnn bno boa bob boe bok bon boo eaa eab eae eak ean eao eba ebb ebe ebk ebn ebo eea eeb eee eek een eeo eka ekb eke eko en- ena enb ene enk enn eno eo- eoa eob eoe eok eon eoo ka- kaa kab kae kak kan kao kba kbb kbe kbk kbn kbo ke- kea keb kee kek ken keo kkb kke kkk kkn kn- kna kne knk knn kno koa kob koe kok kon koo naa nab nae nak nan nao nba nbb nbe nbk nbn nbo ne- nea neb nee nek nen neo nka nke nkk nkn nko nna nnb nne nnk nnn nno no- noa nob noe nok non noo oaa oab oae oak oan oao ob- oba obb obe obk obn obo oea oeb oee oen oeo oka okb oke okk oko on- ona onb one onk onn ono oo- ooa oob ook oon ooo