a-a a-b aaa aab aae aaf aan aas ab- aba abb abe abf abn abs aea aeb aee aef aen aes af- afa afb afe aff afn afs an- ana anb ane anf ann ans as- asa asb ase asf asn ass baa bab bae baf ban bas bba bbb bbe bbf bbn bbs be- bea beb bee bef ben bes bfa bfb bfe bff bfn bfs bna bnb bne bnf bnn bns bsa bsb bse bsf bsn bss eaa eab eae eaf ean eas eba ebb ebe ebf ebn ebs eea eeb eee eef een ees ef- efa efb efe eff efs en- ena enb ene enf enn ens es- esa esb ese esf esn ess faa fab fae faf fan fas fba fbb fbe fbf fbn fbs fea feb fee fef fen fes ffa ffe fff ffn ffs fna fnb fne fnf fnn fns fsa fsb fse fsf fsn fss naa nab nae naf nan nas nba nbb nbe nbf nbn nbs ne- nea neb nee nef nen nes nfa nfb nfe nff nfn nfs nna nnb nne nnf nnn nns nsa nsb nse nsf nsn nss saa sab sae saf san sas sba sbb sbe sbf sbn sbs se- sea seb see sef sen ses sfa sfb sfe sff sfn sfs sna snb sne snf snn sns ss- ssa ssb sse ssf ssn sss