a-a a-b a-i aaa aab aad aaf aai aas ab- aba abb abd abf abi abs ad- ada adb add adf adi ads af- afa afb afd aff afi afs ai- aia aib aid aif aii ais as- asa asb asd asf asi ass baa bab bad baf bai bas bba bbb bbd bbf bbi bbs bda bdb bdd bdf bdi bds bfa bfb bfd bff bfi bfs bi- bia bib bid bif bii bis bsa bsb bsd bsf bsi bss daa dab dad daf dai das dba dbb dbd dbf dbi dbs dda ddb ddd ddf ddi dds dfa dfb dfd dff dfi dfs di- dia dib did dif dii dis dsa dsb dsd dsf dsi dss faa fab fad faf fai fas fba fbb fbd fbf fbi fbs fda fdb fdd fdf fdi fds ffa ffd fff ffi ffs fia fib fid fif fii fis fsa fsb fsd fsf fsi fss i-d i-f ia- iaa iab iad iaf iai ias iba ibb ibd ibf ibi ibs ida idb idd idf idi ids ifa ifb ifd iff ifi ifs iia iib iid iif iii iis is- isa isb isd isf isi iss saa sab sad saf sai sas sba sbb sbd sbf sbi sbs sda sdb sdd sdf sdi sds sfa sfb sfd sff sfi sfs sia sib sid sif sii sis ss- ssa ssb ssd ssf ssi sss