a-a a-c aaa aac aad aaf aao aas ac- aca acc acd acf aco acs ad- ada adc add adf ado ads af- afa afc afd aff afo afs aoa aoc aod aof aoo aos as- asa asc asd asf aso ass c-- caa cac cad caf cao cas cca ccc ccd ccf cco ccs cda cdc cdd cdf cdo cds cfa cfc cfd cff cfo cfs co- coa coc cod cof coo cos csa csc csd csf cso css daa dac dad daf dao das dca dcc dcd dcf dco dcs dda ddc ddd ddf ddo dds dfa dfc dfd dff dfo dfs doa doc dod dof doo dos dsa dsc dsd dsf dso dss faa fac fad faf fao fas fca fcc fcd fcf fco fcs fda fdc fdd fdf fdo fds ffa ffc ffd fff ffo ffs foa foc fof foo fos fsa fsc fsd fsf fso fss oaa oac oad oaf oao oas oc- oca occ ocd ocf oco ocs oda odc odd odf odo ods of- ofa ofc ofd off ofo ofs oo- ooa ooc ood oof ooo oos os- osa osc osd osf oso oss saa sac sad saf sao sas sca scc scd scf sco scs sda sdc sdd sdf sdo sds sfa sfc sfd sff sfo sfs soa soc sod sof soo sos ss- ssa ssc ssd ssf sso sss