bbbb bbbs bffs bfsi bfsr bibb bibi bibo bibs biff bifi biis bio- bioi bios birb biri biro birr birs bis- biso biss bobb bobi bobo bobs boff bofs boi- boii bois boob boof boor boos bor- borf bori boro borr bors bosi boso boss brio bris brob broo bror bros brrr brrs brsb brsr bsff bsfs bsos fbis fbrs ffff ffii ffrr ffss fibs fiff fifi fifo fiii fior fios firs fisi fiss fobs fofo fois foof foos for- forb fori foro forr fors fosb fosi foso foss frib frio fris frob fros frsb frso fsfi fsfo fssf ibfi ibis ibos ibri ibro ibsf ibss ifbb ifis ifor ifrb ifrf ifri ifsb ifso iiii iiio iiis iioi iioo iios iirs iisi iisr iobi ioii ioio ioof iooi iooo ioos iori iors ioso iri- irio iris irob irri irrs irsf isis iso- isof isor isos isri issf issi isso issr isss obbo obis oboi obor obos obri obro obsr obss off- offo offr offs ofor oiii oios oobi ooff oofs oooo ooos oosi orbb orbi orbo orbs orff orfi orfs ori- orif orio oris oro- orof oror oros orri orro orrs orsi orso osii osis osoi osoo osor osos osro ossb ossi osso rbbb rbbr rbbs rbis rbss rib- ribo ribs riff rifs riif riis rios riri rirs risi riso riss rob- robb robi robo robs roff rofo roif roio roir rois roob roof rooi roor roos rori roro rosi roso ross rrif rrrr rsbi rsis rsos s-ib s-ii s-os sbbs sbor sbsi sfio sfor sfos sfro sfss sibi sibo sibs siff sifo sifr sior sios sirf siri siro sirr sirs sisi siss sobo sobr sobs sofi sofo soif soir sois soof soor soos sorb sori soro sorr sors sosi soso soss srfi srib sris sros ssbr ssis ssri ssrs sssb sssf sssi ssss