a-a a-b a-c aaa aab aac aad aan aao aar ab- aba abb abc abd abn abo abr ac- aca acb acc acd acn aco acr ad- ada adb adc add adn ado adr an- ana anb anc and ann ano anr aoa aob aoc aod aon aoo aor ar- ara arb arc ard arn aro arr baa bab bac bad ban bao bar bba bbb bbc bbd bbn bbo bbr bca bcb bcc bcd bcn bco bcr bda bdb bdc bdd bdo bdr bna bnb bnc bnd bnn bno bnr boa bob boc bod bon boo bor bra brb brd brn bro brr c-- caa cab cac cad can cao car cba cbb cbc cbd cbn cbo cbr cca ccb ccc ccd ccn cco ccr cda cdb cdc cdd cdn cdo cdr cn- cna cnb cnc cnd cnn cno cnr co- coa cob coc cod con coo cor cra crb crc crd crn cro crr daa dab dac dad dan dao dar dba dbb dbc dbd dbn dbo dbr dca dcb dcc dcd dcn dco dcr dda ddb ddc ddd ddn ddo ddr dna dnb dnc dnd dnn dno dnr doa dob doc dod don doo dor dra drb drc drd drn dro drr naa nab nac nad nan nao nar nba nbb nbc nbd nbn nbo nbr nca ncb ncc ncd ncn nco ncr nda ndb ndc ndd ndn ndo ndr nna nnb nnc nnn nno no- noa nob noc nod non noo nor nra nrb nrc nrd nrn nro nrr oaa oab oac oad oan oao oar ob- oba obb obc obd obn obo obr oc- oca ocb occ ocd ocn oco ocr oda odb odc odd odn odo odr on- ona onb onc ond onn ono onr oo- ooa oob ooc ood oon ooo oor or- ora orb orc ord orn oro orr ra- raa rab rac rad ran rao rar rba rbb rbc rbd rbn rbo rbr rca rcb rcc rcd rcn rco rcr rda rdb rdc rdd rdn rdo rdr rna rnb rnc rnd rnn rno rnr roa rob roc rod ron roo ror rra rrb rrc rrd rrn rrr