bbbb bibb bibi bibo bio- bioi biot birb biri biro birr birt bito bitt bobb bobi bobo boi- boii boit boob boor boot bor- bori boro borr bort botb boti boto bott brio brit brob broo bror brot brrr btob btor btrt bttb ibot ibri ibro ibtb iiii iiio iiit iioi iioo iitr iitt iobi ioii ioio ioit iooi iooo iori ioto iri- irio irob irri irti itoi itoo itor itri itto obbo obit oboi obor obot obri obro oiii oirt oiti oobi oooo oort ootb orbb orbi orbo ori- orio orit oro- oror orot orri orro orto otit oto- otoo otor otro otti otto rbbb rbbr rib- ribo riot riri riti rito ritt rob- robb robi robo robt roio roir roit roob rooi roor root rori roro rort roti roto rotr rott rrrr tbit tbrb tibi tiit tirb tiri tiro tirr titi tito titt tobi tobo tobt toit toor toot tori toro torr tort toti toto totr tott tri- trib trio trit troi troo trot trtr ttbb tttt