bbb bbk bbr bbs bbt bkb bkk bkr bks bkt brb brk brr brs brt bsb bsk bsr bss bst btb btk btr bts btt k-t kbb kbk kbr kbs kkb kkk kkr kks kkt krk krr krs krt ksb ksk ksr kss kst ktb ktk ktr kts ktt rbb rbk rbr rbs rbt rkb rkk rks rkt rrb rrk rrr rrs rrt rsb rsk rsr rss rst rtb rtk rtr rts rtt sbb sbk sbr sbs sbt sk- skb skk skr sks skt sr- srb srk srr srs srt ss- ssb ssk ssr sss sst stb stk str sts stt tbb tbk tbr tbs tbt tkb tkk tkr tks tkt trb trk trr trs trt tsb tsk tsr tss tst ttb ttk ttr tts ttt