bbb bbc bbk bbo bcb bcc bck bco bcv bkb bkc bkk bko bkv bob boc bok boo bov bvb bvc bvk bvo bvv c-- cbb cbc cbk cbo cbv ccb ccc cck cco ccv ckb ckc cko co- cob coc cok coo cov cvb cvc cvk cvo cvv kbb kbc kbk kbo kcb kcc kck kkb kkc kkk kkv kob koc kok koo kvb kvk kvo kvv ob- obb obc obk obo obv oc- ocb occ ock oco ocv okb okc okk oko oo- oob ooc ook ooo oov ov- ovb ovc ovo ovv vbc vbk vbo vbv vcc vco vkb vob voc vok voo vov vvb vvc vvo vvv