bbbb bbbs bffs bfsi bfsr bfts bftt bibb bibi bibo bibs biff bifi biis bio- bioi bios biot birb biri biro birr birs birt bis- biso biss bist bito bits bitt bobb bobi bobo bobs boff bofs boi- boii bois boit boob boof boor boos boot bor- borf bori boro borr bors bort bosi boso boss bost botb boti boto bots bott brio bris brit brob broo bror bros brot brrr brrs brsb brsr brst bsff bsfs bsos bsts btob btor btrt btss bttb fbis fbrs ffff ffii ffrr ffss fftf fibs fiff fifi fifo fift fiii fior fios firs fisi fiss fist fiti fits fitt fobs fobt fofo fois foof foos foot for- forb fori foro forr fors fort fosb fosi foso foss fost foti foto fots fott frib frio fris frit frob fros frot frsb frso frst fsfi fsfo fssf ftii ftos ftrs ftsr ibfi ibis ibos ibot ibri ibro ibsf ibss ibtb ibts ifbb ifis ifit ifor ifrb ifrf ifri ifsb ifso ifto iiii iiio iiis iiit iioi iioo iios iirs iisi iisr iist iitr iitt iobi ioii ioio ioit ioof iooi iooo ioos iori iors ioso iotf ioto iri- irio iris irob irri irrs irsf irtf irti irts isbt isis isit iso- isof isor isos isri issf issi isso issr isss isti isto istr ists itbs itif itis itof itoi itoo itor itos itrf itri itrs itsf itsi itso ittf itto obbo obis obit oboi obor obos obot obri obro obsr obss obst obts off- offo offr offs ofit ofor ofst oiii oios oirt oist oiti oobi ooff oofs oooo ooos oort oosi oost ootb oots orbb orbi orbo orbs orff orfi orfs ori- orif orio oris orit oro- orof oror oros orot orri orro orrs orsi orso orto orts osii osis osoi osoo osor osos osro ossb ossi osso osti ostr osts otbs otif otis otit oto- otof otoo otor otos otro otrs otso otti otto otts rbbb rbbr rbbs rbis rbss rbst rib- ribo ribs riff rifs rift riif riis rios riot riri rirs risi riso riss rist riti rito rits ritt rob- robb robi robo robs robt roff rofo roif roio roir rois roit roob roof rooi roor roos root rori roro rort rosi roso ross rost roti roto rotr rots rott rrif rrrr rsbi rsis rsos rsts rtbf rtfb rtss rtts s-ib s-ii s-os sbbs sbor sbot sbsi sbst sfio sfor sfos sfro sfss sfts sibi sibo sibs siff sifo sifr sift siit sior sios siot sirf siri siro sirr sirs sirt sisi siss sist sit- siti sito sits sitt sobo sobr sobs sobt sofi sofo soft soif soir sois soit soof soor soos soot sorb sori soro sorr sors sort sosi soso soss sost soto sots srfi srib sris sros srtr ssbr ssis ssit ssot ssri ssrs sssb sssf sssi ssss sstb ssts stbs stib stif stio stir stis stit stob stof stoo stor stos stot stri stro strs stsf stsi stss sttr tbbs tbit tbrb tbst tfot tfrs tfsi tfss tibi tibs tiff tifo tift tiit tios tirb tiri tiro tirr tirs tisb tisi tiso tiss tist titi tito tits titt tobi tobo tobs tobt toff tofi tofo toft tois toit toof toor toos toot torf tori toro torr tors tort tosb tosi toso toss tost toti toto totr tots tott trfr tri- trib trif trio tris trit troi troo tros trot trsi trst trtr tsis tsob tsoi tsos tssf tssi tssr tsst tsts ttbb ttff ttss tttt