a-a aaa aaf aan aao aas af- afa aff afn afo afs an- ana anf ann ano ans aoa aof aon aoo aos as- asa asf asn aso ass faa faf fan fao fas ffa fff ffn ffo ffs fna fnf fnn fns foa fof fon foo fos fsa fsf fsn fso fss naa naf nan nao nas nfa nff nfn nfo nfs nna nnf nnn nno nns no- noa nof non noo nos nsa nsf nsn nso nss oaa oaf oan oao oas of- ofa off ofn ofo ofs on- ona onf onn ono ons oo- ooa oof oon ooo oos os- osa osf osn oso oss saa saf san sao sas sfa sff sfn sfo sfs sna snf snn sno sns soa sof son soo sos ss- ssa ssf ssn sso sss