-er b-u bbb bbc bbe bbk bbr bbu bcb bcc bce bck bcr bcu be- beb bec bee bek ber beu bkb bkc bke bkk bkr brb bre brk brr bru bub buc bue buk bur buu c-- cbb cbc cbe cbk cbr cbu ccb ccc cce cck ccr ccu ce- ceb cec cee cek cer ceu ckb ckc crb crc cre crk crr cru cub cuc cue cuk cur cuu ebb ebc ebe ebk ebr ebu ec- ecb ecc ece eck ecr ecu eeb eec eee eek eer ekb ekc eke ekr eku erb erc ere erk err eru eu- eub euc eue eur kbb kbc kbe kbk kbr kbu kcb kcc kce kck kcr kcu ke- keb kec kee kek ker kkb kkc kke kkk kkr kku krc krk krr kru kub kuc kue kuk kur kuu rbb rbc rbe rbk rbr rbu rcb rcc rce rcr rcu re- reb rec ree rek rer reu rkb rkc rke rkk rku rrb rrc rrk rrr rru rub ruc rue ruk rur ruu ubb ubc ube ubk ubr ubu ucb ucc uce uck ucr ucu ueb uec uee uer ukb ukc uke ukk ukr uku ur- urb urc ure urk urr uru uuc uue uur uuu