a-a a-b aaa aab aad aaf aak aau ab- aba abb abd abf abk abu ad- ada adb add adf adk adu af- afa afb afd aff afk afu aka akb akd akk aku au- aua aub aud auf auk b-u baa bab bad baf bak bau bba bbb bbd bbf bbk bbu bda bdb bdd bdf bdk bdu bfa bfb bfd bff bfu bka bkb bkf bkk bua bub bud buf buk buu daa dab dad daf dak dau dba dbb dbd dbf dbk dbu dda ddb ddd ddf ddk ddu dfa dfb dfd dff dfk dfu dka dkb dkk dku dua dub dud duf duk faa fab fad faf fak fau fba fbb fbd fbf fbk fbu fda fdb fdd fdf fdk fdu ffa ffd fff ffk ffu fka fkb fkf fkk fua fub fud fuf fuk fuu ka- kaa kab kad kaf kak kau kba kbb kbd kbf kbk kbu kda kdb kdf kdk kdu kfa kfd kff kfu kkb kkk kku kub kud kuk kuu ua- uaa uab uad uaf uak uau uba ubb ubf ubk ubu uda udb udd udf udk udu ufa ufd uff ufu uka ukb ukf ukk uku uua uuu