b-u bbb bbl bbn bbr bbt bbu blb bll bln blr blt blu bnb bnl bnn bnr bnt bnu brb brl brn brr brt bru btb btl btn btr btt btu bub bul bun bur but buu lbb lbl lbr lbt lbu llb lll lln llr llt llu lnb lnl lnn lnr lnt lnu lrb lrn lrr lrt lru ltb ltl ltr ltt ltu lub lul lun lur lut luu nbb nbl nbn nbr nbt nbu nlb nll nln nlr nlt nlu nnb nnl nnn nnt nnu nrb nrl nrn nrr nrt nru ntb ntn ntr ntt ntu nub nul nun nur nut nuu rbb rbl rbn rbr rbt rbu rll rln rlr rlt rlu rnb rnn rnr rnt rnu rrb rrl rrn rrr rrt rru rtb rtl rtn rtr rtt rtu rub run rur rut ruu tbb tbl tbn tbr tbt tbu tll tln tlr tlt tlu tnb tnl tnn tnr tnt trb trl trn trr trt tru ttb ttl ttn ttr ttt ttu tub tul tun tur tut tuu ubb ubl ubn ubr ubt ubu ulb ull uln ulr ult ulu un- unb unl unn unr unt unu ur- urb url urn urr urt uru utb utl utn utr utt utu uun uur uut uuu