ffff ffii ffss fftf fiff fifi fifo fift fiii fios fisi fiss fist fiti fits fitt fofo fois foof foos foot fosi foso foss fost foti foto fots fott fsfi fsfo fssf ftii ftos ifis ifit ifso ifto iiii iiio iiis iiit iioi iioo iios iisi iist iitt ioii ioio ioit ioof iooi iooo ioos ioso iotf ioto isis isit iso- isof isos issf issi isso isss isti isto ists itif itis itof itoi itoo itos itsf itsi itso ittf itto off- offo offs ofit ofst oiii oios oist oiti ooff oofs oooo ooos oosi oost oots osii osis osoi osoo osos ossi osso osti osts otif otis otit oto- otof otoo otos otso otti otto otts s-ii s-os sfio sfos sfss sfts siff sifo sift siit sios siot sisi siss sist sit- siti sito sits sitt sofi sofo soft soif sois soit soof soos soot sosi soso soss sost soto sots ssis ssit ssot sssf sssi ssss ssts stif stio stis stit stof stoo stos stot stsf stsi stss tfot tfsi tfss tiff tifo tift tiit tios tisi tiso tiss tist titi tito tits titt toff tofi tofo toft tois toit toof toos toot tosi toso toss tost toti toto tots tott tsis tsoi tsos tssf tssi tsst tsts ttff ttss tttt