a-fu aaaa aaab aaaf aaas aaba aabb aafa aafb aaff aasa aasf aass aasu aaus abaa abab abaf abas abau abb- abba abbb abbs abff abs- absa absf abss absu abua abuf abus afaa afbs affa affs afsa afsb afua afus asaa asab asaf asas asau asba asbu asfa assa asss assu asub asus auaa aufs ausa ausu baaa baaf baas baba babb babs babu baff basa basf bass basu bau- bauf bbas bbau bbbb bbbs bfas bffs bsaa bsas bsfa bsff bsfs buba bubb bubs bubu buff busa buss busu buus faaa faas faba fabs fabu fafa faff fasa fass fbus ffff ffsa ffss fsas fssa fssf fubb fubs fubu fuff fufu fusa fuss fusu saab saaf saas saba sabb sabs sabu safa safb saff safu sasa sasf sass saua sauf saus sbaa sbas sbbs sbsa sbus sfas sfba sfss sfsu ssaa ssab ssas ssau sssa sssb sssf ssss suas sub- suba subb subs suf- sufa suff sufs sufu sus- susa suss susu suus uafa uasa uaua ubba uffa us-a usaa usaf usas usba usbs usfa usfs ussa ussb ussf usss ussu usua usus uuuu