bbbb bbrc bcbc bccc bcor bcru bcuc bobb bobo bobu boco bocu boob booc boor bor- boro borr boru bour brcb brob broc broo bror brou brrr bruc bubb bubo bubu bucc buco bucu bur- burb buro burr buru c-bo cbbc cbcc cbcr cbcu ccbc cccb cccc cccu ccob ccoc ccrc ccuc cobb cobo cobu coco cocu coob cor- corb corc coro corr coub cour crbc crbu crcc crcr crob croc croo cror crub cub- cubb cucc curb curo curr obbo obor obro ocbc occc ocro ocrr ocur oocr oooo orbb orbo orbu orco oro- oror orro orub oucc our- ouro ouu- rbbb rbbr rcbc rcbo rccb rccc rob- robb robo robu rocc roco roob roor rorc roro roru roub rrrr rubb rubu rurc ruro ruru ubbo uboc ucbc ucrc uocc uor- uro- uroo urur uuoc uuuu