-th bbb bbc bbh bbo bbt bcb bcc bch bco bct bhb bhc bhh bho bht bob boc boh boo bot btb btc bth bto btt c-- cbb cbc cbh cbo cbt ccb ccc cch cco cct ch- chb chc chh cho cht co- cob coc coh coo cot ctb ctc cth cto ctt hbb hbc hbh hbo hbt hcb hcc hch hco hct hhb hhc hhh hho hht hob hoc hoh hoo hot htb htc hth hto htt ob- obb obc obh obo obt oc- ocb occ och oco oct ohc ohh oho oht oo- oob ooc ooh ooo oot ot- otb otc oth oto ott tbb tbc tbh tbo tbt tcb tcc tch tco tct th- thb thc thh tho tht to- tob toc toh too tot ttb ttc tth tto ttt