-er b-u bbb bbc bbe bbk bbo bbr bbt bbu bcb bcc bce bck bco bcr bct bcu be- beb bec bee bek beo ber bet beu bkb bkc bke bkk bko bkr bkt bob boc boe bok boo bor bot bou brb bre brk bro brr brt bru btb btc bte btk bto btr btt btu bub buc bue buk buo bur but buu c-- cbb cbc cbe cbk cbo cbr cbt cbu ccb ccc cce cck cco ccr cct ccu ce- ceb cec cee cek ceo cer cet ceu ckb ckc cko ckt co- cob coc coe cok coo cor cot cou crb crc cre crk cro crr crt cru ctb ctc cte ctk cto ctr ctt ctu cub cuc cue cuk cuo cur cut cuu ebb ebc ebe ebk ebo ebr ebt ebu ec- ecb ecc ece eck eco ecr ect ecu eeb eec eee eek eeo eer eet ekb ekc eke eko ekr ekt eku eo- eob eoc eoe eok eoo eor eot eou erb erc ere erk ero err ert eru etb etc ete etk eto etr ett etu eu- eub euc eue eur eut k-t kbb kbc kbe kbk kbo kbr kbu kcb kcc kce kck kcr kct kcu ke- keb kec kee kek keo ker ket kkb kkc kke kkk kkr kkt kku kob koc koe kok koo kor kot kou krc krk kro krr krt kru ktb ktc kte ktk kto ktr ktt ktu kub kuc kue kuk kur kut kuu ob- obb obc obe obk obo obr obt obu oc- ocb occ ock oco ocr oct ocu oeb oec oee oeo oer oet okb okc oke okk oko okr oku oo- oob ooc ook ooo oor oot or- orb orc ore ork oro orr ort oru ot- otb otc ote otk oto otr ott otu ou- ouc oue ouk ouo our out rbb rbc rbe rbk rbo rbr rbt rbu rcb rcc rce rco rcr rct rcu re- reb rec ree rek reo rer ret reu rkb rkc rke rkk rko rkt rku rob roc roe rok roo ror rot rou rrb rrc rrk rrr rrt rru rtb rtc rte rtk rto rtr rtt rtu rub ruc rue ruk ruo rur rut ruu tbb tbc tbe tbk tbo tbr tbt tbu tcb tcc tce tck tco tcr tct tcu te- teb tec tee tek teo ter tet teu tkb tkc tke tkk tko tkr tkt to- tob toc toe tok too tor tot tou trb trc tre trk tro trr trt tru ttb ttc tte ttk tto ttr ttt ttu tub tuc tue tuk tuo tur tut tuu ubb ubc ube ubk ubo ubr ubt ubu ucb ucc uce uck uco ucr uct ucu ueb uec uee uer uet ukb ukc uke ukk ukr uku uob uoc uoe uok uoo uor uot ur- urb urc ure urk uro urr urt uru utb utc ute utk uto utr utt utu uuc uue uur uut uuu