bbbb bftt bibb bibi bibo biff bifi bio- bioi biot birb biri biro birr birt bito bitt bobb bobi bobo boff boi- boii boit boob boof boor boot bor- borf bori boro borr bort botb boti boto bott brio brit brob broo bror brot brrr btob btor btrt bttb ffff ffii ffrr fftf fiff fifi fifo fift fiii fior fiti fitt fobt fofo foof foot for- forb fori foro forr fort foti foto fott frib frio frit frob frot ftii ibfi ibot ibri ibro ibtb ifbb ifit ifor ifrb ifrf ifri ifto iiii iiio iiit iioi iioo iitr iitt iobi ioii ioio ioit ioof iooi iooo iori iotf ioto iri- irio irob irri irtf irti itif itof itoi itoo itor itrf itri ittf itto obbo obit oboi obor obot obri obro off- offo offr ofit ofor oiii oirt oiti oobi ooff oooo oort ootb orbb orbi orbo orff orfi ori- orif orio orit oro- orof oror orot orri orro orto otif otit oto- otof otoo otor otro otti otto rbbb rbbr rib- ribo riff rift riif riot riri riti rito ritt rob- robb robi robo robt roff rofo roif roio roir roit roob roof rooi roor root rori roro rort roti roto rotr rott rrif rrrr rtbf rtfb tbit tbrb tfot tibi tiff tifo tift tiit tirb tiri tiro tirr titi tito titt tobi tobo tobt toff tofi tofo toft toit toof toor toot torf tori toro torr tort toti toto totr tott trfr tri- trib trif trio trit troi troo trot trtr ttbb ttff tttt