bbbb bbrc bcbc bccc bcor bctc bobb bobo boco boob booc boor boot bor- boro borr bort botb boto bott brcb brob broc broo bror brot brrr brtc btcc btob btor btrc btrt bttb c-bo cbbc cbcc cbcr cbct cbot cbrt cbtc ccbc cccb cccc ccob ccoc ccrc ccrt cctb cctc cctt cobb cobo coco coct coob coot cor- corb corc coro corr cort cotb cotc coto cott crbc crcc crcr crob croc croo cror crot crrt crtc ctor ctot ctrc obbo obor obot obro ocbc occc occt ocro ocrr oct- octo oocr oooo oort ootb orbb orbo orco oro- oror orot orro ortc orto oto- otoo otor otro otto rbbb rbbr rcbc rcbo rccb rccc rctc rob- robb robo robt rocc roco roob roor root rorc roro rort rotc roto rotr rott rrrr rtcc tbcb tbcc tbrb tccc tctc tobo tobt toco toor toot torc toro torr tort totc toto totr tott trcc troc troo trot trtc trtr ttbb tttt