a-a a-b aaa aab aad aar aau ab- aba abb abd abr abu ad- ada adb add adr adu ar- ara arb ard arr aru au- aua aub aud aur b-u baa bab bad bar bau bba bbb bbd bbr bbu bda bdb bdd bdr bdu bra brb brd brr bru bua bub bud bur buu daa dab dad dar dau dba dbb dbd dbr dbu dda ddb ddd ddr ddu dra drb drd drr dru dua dub dud dur ra- raa rab rad rar rau rba rbb rbd rbr rbu rda rdb rdd rdr rdu rra rrb rrd rrr rru rua rub rud rur ruu ua- uaa uab uad uar uau uba ubb ubr ubu uda udb udd udr udu ur- ura urb urd urr uru uua uur uuu