a-a a-b aaa aab aae aak aao ab- aba abb abe abk abo aea aeb aee aek aeo aka akb ake akk ako aoa aob aoe aok aoo baa bab bae bak bao bba bbb bbe bbk bbo be- bea beb bee bek beo bka bkb bke bkk bko boa bob boe bok boo eaa eab eae eak eao eba ebb ebe ebk ebo eea eeb eee eek eeo eka ekb eke eko eo- eoa eob eoe eok eoo ka- kaa kab kae kak kao kba kbb kbe kbk kbo ke- kea keb kee kek keo kkb kke kkk koa kob koe kok koo oaa oab oae oak oao ob- oba obb obe obk obo oea oeb oee oeo oka okb oke okk oko oo- ooa oob ook ooo