-er b-u bbb bbc bbe bbr bbt bbu bcb bcc bce bcr bct bcu be- beb bec bee ber bet beu brb bre brr brt bru btb btc bte btr btt btu bub buc bue bur but buu c-- cbb cbc cbe cbr cbt cbu ccb ccc cce ccr cct ccu ce- ceb cec cee cer cet ceu crb crc cre crr crt cru ctb ctc cte ctr ctt ctu cub cuc cue cur cut cuu ebb ebc ebe ebr ebt ebu ec- ecb ecc ece ecr ect ecu eeb eec eee eer eet erb erc ere err ert eru etb etc ete etr ett etu eu- eub euc eue eur eut rbb rbc rbe rbr rbt rbu rcb rcc rce rcr rct rcu re- reb rec ree rer ret reu rrb rrc rrr rrt rru rtb rtc rte rtr rtt rtu rub ruc rue rur rut ruu tbb tbc tbe tbr tbt tbu tcb tcc tce tcr tct tcu te- teb tec tee ter tet teu trb trc tre trr trt tru ttb ttc tte ttr ttt ttu tub tuc tue tur tut tuu ubb ubc ube ubr ubt ubu ucb ucc uce ucr uct ucu ueb uec uee uer uet ur- urb urc ure urr urt uru utb utc ute utr utt utu uuc uue uur uut uuu