b-u bbb bbc bbk bbr bbs bbt bbu bcb bcc bck bcr bcs bct bcu bkb bkc bkk bkr bks bkt brb brk brr brs brt bru bsb bsc bsk bsr bss bst bsu btb btc btk btr bts btt btu bub buc buk bur bus but buu c-- cbb cbc cbk cbr cbs cbt cbu ccb ccc cck ccr ccs cct ccu ckb ckc cks ckt crb crc crk crr crs crt cru csb csc csk csr css cst csu ctb ctc ctk ctr cts ctt ctu cub cuc cuk cur cus cut cuu k-t kbb kbc kbk kbr kbs kbu kcb kcc kck kcr kcs kct kcu kkb kkc kkk kkr kks kkt kku krc krk krr krs krt kru ksb ksc ksk ksr kss kst ksu ktb ktc ktk ktr kts ktt ktu kub kuc kuk kur kus kut kuu rbb rbc rbk rbr rbs rbt rbu rcb rcc rcr rcs rct rcu rkb rkc rkk rks rkt rku rrb rrc rrk rrr rrs rrt rru rsb rsc rsk rsr rss rst rsu rtb rtc rtk rtr rts rtt rtu rub ruc ruk rur rus rut ruu sbb sbc sbk sbr sbs sbt sbu scb scc sck scr scs sct scu sk- skb skc skk skr sks skt sku sr- srb src srk srr srs srt ss- ssb ssc ssk ssr sss sst ssu stb stc stk str sts stt stu sub suc suk sur sus sut suu tbb tbc tbk tbr tbs tbt tbu tcb tcc tck tcr tcs tct tcu tkb tkc tkk tkr tks tkt trb trc trk trr trs trt tru tsb tsc tsk tsr tss tst tsu ttb ttc ttk ttr tts ttt ttu tub tuc tuk tur tus tut tuu ubb ubc ubk ubr ubs ubt ubu ucb ucc uck ucr ucs uct ucu ukb ukc ukk ukr uku ur- urb urc urk urr urs urt uru usb usc usk usr uss ust usu utb utc utk utr uts utt utu uuc uur uus uut uuu