-er bbb bbc bbe bbk bbr bcb bcc bce bck bcr bcv be- beb bec bee bek ber bev bkb bkc bke bkk bkr bkv brb bre brk brr brv bvb bvc bve bvk bvr bvv c-- cbb cbc cbe cbk cbr cbv ccb ccc cce cck ccr ccv ce- ceb cec cee cek cer cev ckb ckc crb crc cre crk crr crv cvb cvc cve cvk cvr cvv ebb ebc ebe ebk ebr ebv ec- ecb ecc ece eck ecr ecv eeb eec eee eek eer eev ekb ekc eke ekr ekv erb erc ere erk err erv evb evc eve evr evv kbb kbc kbe kbk kbr kcb kcc kce kck kcr ke- keb kec kee kek ker kev kkb kkc kke kkk kkr kkv krc krk krr krv kvb kvk kvr kvv rbb rbc rbe rbk rbr rcb rcc rce rcr rcv re- reb rec ree rek rer rev rkb rkc rke rkk rkv rrb rrc rrk rrr rvb rvc rve rvr rvv v-e vbc vbk vbr vbv vcc vce vcr veb vec vee vek ver vkb vrb vrc vre vrk vrr vvb vvc vvr vvv