b-u bbb bbl bbn bbr bbu blb bll bln blr blu bnb bnl bnn bnr bnu brb brl brn brr bru bub bul bun bur buu lbb lbl lbr lbu llb lll lln llr llu lnb lnl lnn lnr lnu lrb lrn lrr lru lub lul lun lur luu nbb nbl nbn nbr nbu nlb nll nln nlr nlu nnb nnl nnn nnu nrb nrl nrn nrr nru nub nul nun nur nuu rbb rbl rbn rbr rbu rll rln rlr rlu rnb rnn rnr rnu rrb rrl rrn rrr rru rub run rur ruu ubb ubl ubn ubr ubu ulb ull uln ulr ulu un- unb unl unn unr unu ur- urb url urn urr uru uun uur uuu