bbbb bbbs bibb bibi bibo bibs biis bio- bioi bios birb biri biro birr birs bis- biso biss bobb bobi bobo bobs boi- boii bois boob boor boos bor- bori boro borr bors bosi boso boss brio bris brob broo bror bros brrr brrs brsb brsr bsos ibis ibos ibri ibro ibss iiii iiio iiis iioi iioo iios iirs iisi iisr iobi ioii ioio iooi iooo ioos iori iors ioso iri- irio iris irob irri irrs isis iso- isor isos isri issi isso issr isss obbo obis oboi obor obos obri obro obsr obss oiii oios oobi oooo ooos oosi orbb orbi orbo orbs ori- orio oris oro- 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 riis rios riri rirs risi riso riss rob- robb robi robo robs roio roir rois roob rooi roor roos rori roro rosi roso ross rrrr rsbi rsis rsos s-ib s-ii s-os sbbs sbor sbsi sibi sibo sibs sior sios siri siro sirr sirs sisi siss sobo sobr sobs soir sois soor soos sorb sori soro sorr sors sosi soso soss srib sris sros ssbr ssis ssri ssrs sssb sssi ssss