a-a a-b aaa aab aad aae aak ab- aba abb abd abe abk ad- ada adb add ade adk aea aeb aed aee aek aka akb akd ake akk baa bab bad bae bak bba bbb bbd bbe bbk bda bdb bdd bde bdk be- bea beb bed bee bek bka bkb bke bkk daa dab dad dae dak dba dbb dbd dbe dbk dda ddb ddd dde ddk de- dea deb ded dee dek dka dkb dke dkk eaa eab ead eae eak eba ebb ebd ebe ebk ed- eda edb edd ede edk eea eeb eed eee eek eka ekb ekd eke ka- kaa kab kad kae kak kba kbb kbd kbe kbk kda kdb kde kdk ke- kea keb ked kee kek kkb kke kkk