-er b-u bbb bbc bbe bbg bbk bbo bbr bbu bcb bcc bce bcg bck bco bcr bcu be- beb bec bee beg bek beo ber beu bgb bgc bge bgg bgk bgo bgr bgu bkb bkc bke bkg bkk bko bkr bob boc boe bog bok boo bor bou brb bre brg brk bro brr bru bub buc bue bug buk buo bur buu c-- cbb cbc cbe cbg cbk cbo cbr cbu ccb ccc cce ccg cck cco ccr ccu ce- ceb cec cee ceg cek ceo cer ceu cgb cgc cge cgg cgo cgr cgu ckb ckc cko co- cob coc coe cog cok coo cor cou crb crc cre crg crk cro crr cru cub cuc cue cug cuk cuo cur cuu ebb ebc ebe ebg ebk ebo ebr ebu ec- ecb ecc ece ecg eck eco ecr ecu eeb eec eee eeg eek eeo eer egb egc ege egg ego egr egu ekb ekc eke ekg eko ekr eku eo- eob eoc eoe eog eok eoo eor eou erb erc ere erg erk ero err eru eu- eub euc eue eug eur gbc gbe gbg gbk gbo gbr gbu gcb gcc gce gcg gck gco gcr gcu ge- geb gec gee geg gek geo ger geu ggb ggc ggg ggo ggr ggu gkb gko gob goc goe gog gok goo gor gou grb grc gre grg grk gro grr gru gu- gub guc gue gug guk guo gur guu kbb kbc kbe kbk kbo kbr kbu kcb kcc kce kcg kck kcr kcu ke- keb kec kee keg kek keo ker kgb kgc kgo kgu kkb kkc kke kkk kkr kku kob koc koe kog kok koo kor kou krc krg krk kro krr kru kub kuc kue kug kuk kur kuu ob- obb obc obe obg obk obo obr obu oc- ocb occ ocg ock oco ocr ocu oeb oec oee oeg oeo oer ogc oge ogg ogo okb okc oke okg okk oko okr oku oo- oob ooc oog ook ooo oor or- orb orc ore org ork oro orr oru ou- ouc oue ouk ouo our rbb rbc rbe rbg rbk rbo rbr rbu rcb rcc rce rcg rco rcr rcu re- reb rec ree reg rek reo rer reu rgb rgc rge rgg rgk rgo rgr rkb rkc rke rkg rkk rko rku rob roc roe rog rok roo ror rou rrb rrc rrg rrk rrr rru rub ruc rue rug ruk ruo rur ruu ubb ubc ube ubg ubk ubo ubr ubu ucb ucc uce ucg uck uco ucr ucu ueb uec uee ueg uer ugb ugc uge ugg ugk ugo ugr ugu ukb ukc uke ukk ukr uku uob uoc uoe uog uok uoo uor ur- urb urc ure urg urk uro urr uru uuc uue uug uur uuu