a-a a-b aaa aab aad aae aak aao ab- aba abb abd abe abk abo ad- ada adb add ade adk ado aea aeb aed aee aek aeo aka akb akd ake akk ako aoa aob aod aoe aok aoo baa bab bad bae bak bao bba bbb bbd bbe bbk bbo bda bdb bdd bde bdk bdo be- bea beb bed bee bek beo bka bkb bke bkk bko boa bob bod boe bok boo daa dab dad dae dak dao dba dbb dbd dbe dbk dbo dda ddb ddd dde ddk ddo de- dea deb ded dee dek deo dka dkb dke dkk dko doa dob dod doe dok doo eaa eab ead eae eak eao eba ebb ebd ebe ebk ebo ed- eda edb edd ede edk edo eea eeb eed eee eek eeo eka ekb ekd eke eko eo- eoa eob eod eoe eok eoo ka- kaa kab kad kae kak kao kba kbb kbd kbe kbk kbo kda kdb kde kdk kdo ke- kea keb ked kee kek keo kkb kke kkk koa kob kod koe kok koo oaa oab oad oae oak oao ob- oba obb obd obe obk obo oda odb odd ode odo oea oeb oed oee oeo oka okb okd oke okk oko oo- ooa oob ood ook ooo