a-a a-b aaa aab aad aae aaf aas ab- aba abb abd abe abf abs ad- ada adb add ade adf ads aea aeb aed aee aef aes af- afa afb afd afe aff afs as- asa asb asd ase asf ass baa bab bad bae baf bas bba bbb bbd bbe bbf bbs bda bdb bdd bde bdf bds be- bea beb bed bee bef bes bfa bfb bfd bfe bff bfs bsa bsb bsd bse bsf bss daa dab dad dae daf das dba dbb dbd dbe dbf dbs dda ddb ddd dde ddf dds de- dea deb ded dee def des dfa dfb dfd dfe dff dfs dsa dsb dsd dse dsf dss eaa eab ead eae eaf eas eba ebb ebd ebe ebf ebs ed- eda edb edd ede edf eds eea eeb eed eee eef ees ef- efa efb efd efe eff efs es- esa esb esd ese esf ess faa fab fad fae faf fas fba fbb fbd fbe fbf fbs fda fdb fdd fde fdf fds fea feb fed fee fef fes ffa ffd ffe fff ffs fsa fsb fsd fse fsf fss saa sab sad sae saf sas sba sbb sbd sbe sbf sbs sda sdb sdd sde sdf sds se- sea seb sed see sef ses sfa sfb sfd sfe sff sfs ss- ssa ssb ssd sse ssf sss