bbb bbc bbn bbo bbt bcb bcc bcn bco bct bnb bnc bnn bno bnt bob boc bon boo bot btb btc btn bto btt c-- cbb cbc cbn cbo cbt ccb ccc ccn cco cct cn- cnb cnc cnn cno cnt co- cob coc con coo cot ctb ctc ctn cto ctt nbb nbc nbn nbo nbt ncb ncc ncn nco nct nnb nnc nnn nno nnt no- nob noc non noo not ntb ntc ntn nto ntt ob- obb obc obn obo obt oc- ocb occ ocn oco oct on- onb onc onn ono ont oo- oob ooc oon ooo oot ot- otb otc otn oto ott tbb tbc tbn tbo tbt tcb tcc tcn tco tct tnb tnc tnn tno tnt to- tob toc ton too tot ttb ttc ttn tto ttt