a-a a-b aaa aab aad aan aao aar ab- aba abb abd abn abo abr ad- ada adb add adn ado adr an- ana anb and ann ano anr aoa aob aod aon aoo aor ar- ara arb ard arn aro arr baa bab bad ban bao bar bba bbb bbd bbn bbo bbr bda bdb bdd bdo bdr bna bnb bnd bnn bno bnr boa bob bod bon boo bor bra brb brd brn bro brr daa dab dad dan dao dar dba dbb dbd dbn dbo dbr dda ddb ddd ddn ddo ddr dna dnb dnd dnn dno dnr doa dob dod don doo dor dra drb drd drn dro drr naa nab nad nan nao nar nba nbb nbd nbn nbo nbr nda ndb ndd ndn ndo ndr nna nnb nnn nno no- noa nob nod non noo nor nra nrb nrd nrn nro nrr oaa oab oad oan oao oar ob- oba obb obd obn obo obr oda odb odd odn odo odr on- ona onb ond onn ono onr oo- ooa oob ood oon ooo oor or- ora orb ord orn oro orr ra- raa rab rad ran rao rar rba rbb rbd rbn rbo rbr rda rdb rdd rdn rdo rdr rna rnb rnd rnn rno rnr roa rob rod ron roo ror rra rrb rrd rrn rrr