a-a a-b aaa aab aad aae aaf aao ab- aba abb abd abe abf abo ad- ada adb add ade adf ado aea aeb aed aee aef aeo af- afa afb afd afe aff afo aoa aob aod aoe aof aoo baa bab bad bae baf bao bba bbb bbd bbe bbf bbo bda bdb bdd bde bdf bdo be- bea beb bed bee bef beo bfa bfb bfd bfe bff bfo boa bob bod boe bof boo daa dab dad dae daf dao dba dbb dbd dbe dbf dbo dda ddb ddd dde ddf ddo de- dea deb ded dee def deo dfa dfb dfd dfe dff dfo doa dob dod doe dof doo eaa eab ead eae eaf eao eba ebb ebd ebe ebf ebo ed- eda edb edd ede edf edo eea eeb eed eee eef eeo ef- efa efb efd efe eff efo eo- eoa eob eod eoe eof eoo faa fab fad fae faf fao fba fbb fbd fbe fbf fbo fda fdb fdd fde fdf fdo fea feb fed fee fef feo ffa ffd ffe fff ffo foa fob foe fof foo oaa oab oad oae oaf oao ob- oba obb obd obe obf obo oda odb odd ode odf odo oea oeb oed oee oef oeo of- ofa ofb ofd ofe off ofo oo- ooa oob ood oof ooo