a-a a-b a-c aaa aab aac aad aaf aah aao ab- aba abb abc abd abf abh abo ac- aca acb acc acd acf ach aco ad- ada adb adc add adf adh ado af- afa afb afc afd aff afh afo aha ahb ahc ahd ahf ahh aho aoa aob aoc aod aof aoh aoo baa bab bac bad baf bah bao bba bbb bbc bbd bbf bbh bbo bca bcb bcc bcd bcf bch bco bda bdb bdc bdd bdf bdh bdo bfa bfb bfc bfd bff bfh bfo bha bhb bhc bhd bhf bhh bho boa bob boc bod bof boh boo c-- caa cab cac cad caf cah cao cba cbb cbc cbd cbf cbh cbo cca ccb ccc ccd ccf cch cco cda cdb cdc cdd cdf cdh cdo cfa cfb cfc cfd cff cfh cfo ch- cha chb chc chd chf chh cho co- coa cob coc cod cof coh coo daa dab dac dad daf dah dao dba dbb dbc dbd dbf dbh dbo dca dcb dcc dcd dcf dco dda ddb ddc ddd ddf ddh ddo dfa dfb dfc dfd dff dfh dfo dh- dha dhb dhc dhd dhf dhh dho doa dob doc dod dof doh doo faa fab fac fad faf fah fao fba fbb fbc fbd fbf fbh fbo fca fcb fcc fcd fcf fco fda fdb fdc fdd fdf fdh fdo ffa ffc ffd fff ffh ffo fha fhb fhc fhf fhh fho foa fob foc fof foh foo haa hab hac had haf hah hao hba hbb hbc hbd hbf hbh hbo hca hcb hcc hcd hcf hch hco hda hdb hdc hdd hdf hdh hdo hfa hfb hfc hfd hff hfh hfo hha hhb hhc hhd hhf hhh hho hoa hob hoc hod hof hoh hoo oaa oab oac oad oaf oah oao ob- oba obb obc obd obf obh obo oc- oca ocb occ ocd ocf och oco oda odb odc odd odf odh odo of- ofa ofb ofc ofd off ofo oha ohc ohd ohf ohh oho oo- ooa oob ooc ood oof ooh ooo