a-a a-b aaa aab aad aan aar ab- aba abb abd abn abr ad- ada adb add adn adr an- ana anb and ann anr ar- ara arb ard arn arr baa bab bad ban bar bba bbb bbd bbn bbr bda bdb bdd bdr bna bnb bnd bnn bnr bra brb brd brn brr daa dab dad dan dar dba dbb dbd dbn dbr dda ddb ddd ddn ddr dna dnb dnd dnn dnr dra drb drd drn drr naa nab nad nan nar nba nbb nbd nbn nbr nda ndb ndd ndn ndr nna nnb nnn nra nrb nrd nrn nrr ra- raa rab rad ran rar rba rbb rbd rbn rbr rda rdb rdd rdn rdr rna rnb rnd rnn rnr rra rrb rrd rrn rrr