b-u bbb bbk bbr bbt bbu bkb bkk bkr bkt brb brk brr brt bru btb btk btr btt btu bub buk bur but buu k-t kbb kbk kbr kbu kkb kkk kkr kkt kku krk krr krt kru ktb ktk ktr ktt ktu kub kuk kur kut kuu rbb rbk rbr rbt rbu rkb rkk rkt rku rrb rrk rrr rrt rru rtb rtk rtr rtt rtu rub ruk rur rut ruu tbb tbk tbr tbt tbu tkb tkk tkr tkt trb trk trr trt tru ttb ttk ttr ttt ttu tub tuk tur tut tuu ubb ubk ubr ubt ubu ukb ukk ukr uku ur- urb urk urr urt uru utb utk utr utt utu uur uut uuu