bbb bbc bbe bbo bbt bcb bcc bce bco bct be- beb bec bee beo bet bob boc boe boo bot btb btc bte bto btt c-- cbb cbc cbe cbo cbt ccb ccc cce cco cct ce- ceb cec cee ceo cet co- cob coc coe coo cot ctb ctc cte cto ctt ebb ebc ebe ebo ebt ec- ecb ecc ece eco ect eeb eec eee eeo eet eo- eob eoc eoe eoo eot etb etc ete eto ett ob- obb obc obe obo obt oc- ocb occ oco oct oeb oec oee oeo oet oo- oob ooc ooo oot ot- otb otc ote oto ott tbb tbc tbe tbo tbt tcb tcc tce tco tct te- teb tec tee teo tet to- tob toc toe too tot ttb ttc tte tto ttt