-er b-u bbb bbc bbe bbk bbr bbt bbu bcb bcc bce bck bcr bct bcu be- beb bec bee bek ber bet beu bkb bkc bke bkk bkr bkt brb bre brk brr brt bru btb btc bte btk btr btt btu bub buc bue buk bur but buu c-- cbb cbc cbe cbk cbr cbt cbu ccb ccc cce cck ccr cct ccu ce- ceb cec cee cek cer cet ceu ckb ckc ckt crb crc cre crk crr crt cru ctb ctc cte ctk ctr ctt ctu cub cuc cue cuk cur cut cuu ebb ebc ebe ebk ebr ebt ebu ec- ecb ecc ece eck ecr ect ecu eeb eec eee eek eer eet ekb ekc eke ekr ekt eku erb erc ere erk err ert eru etb etc ete etk etr ett etu eu- eub euc eue eur eut k-t kbb kbc kbe kbk kbr kbu kcb kcc kce kck kcr kct kcu ke- keb kec kee kek ker ket kkb kkc kke kkk kkr kkt kku krc krk krr krt kru ktb ktc kte ktk ktr ktt ktu kub kuc kue kuk kur kut kuu rbb rbc rbe rbk rbr rbt rbu rcb rcc rce rcr rct rcu re- reb rec ree rek rer ret reu rkb rkc rke rkk rkt rku rrb rrc rrk rrr rrt rru rtb rtc rte rtk rtr rtt rtu rub ruc rue ruk rur rut ruu tbb tbc tbe tbk tbr tbt tbu tcb tcc tce tck tcr tct tcu te- teb tec tee tek ter tet teu tkb tkc tke tkk tkr tkt trb trc tre trk trr trt tru ttb ttc tte ttk ttr ttt ttu tub tuc tue tuk tur tut tuu ubb ubc ube ubk ubr ubt ubu ucb ucc uce uck ucr uct ucu ueb uec uee uer uet ukb ukc uke ukk ukr uku ur- urb urc ure urk urr urt uru utb utc ute utk utr utt utu uuc uue uur uut uuu