a-a a-b a-i aaa aab aai aan aar aas ab- aba abb abi abn abr abs ai- aia aib aii ain air ais an- ana anb ani ann anr ans ar- ara arb ari arn arr ars as- asa asb asi asn asr ass baa bab bai ban bar bas bba bbb bbi bbn bbr bbs bi- bia bib bii bin bir bis bna bnb bni bnn bnr bns bra brb bri brn brr brs bsa bsb bsi bsn bsr bss ia- iaa iab iai ian iar ias iba ibb ibi ibn ibr ibs iia iib iii iin iir iis in- ina inb ini inn inr ins ir- ira irb iri irn irr irs is- isa isb isi isn isr iss n-i naa nab nai nan nar nas nba nbb nbi nbn nbr nbs nia nib nii nin nir nis nna nnb nni nnn nns nra nrb nri nrn nrr nrs nsa nsb nsi nsn nsr nss ra- raa rab rai ran rar ras rba rbb rbi rbn rbr rbs ria rib rii rin rir ris rna rnb rni rnn rnr rns rra rrb rri rrn rrr rrs rsa rsb rsi rsn rsr rss saa sab sai san sar sas sba sbb sbi sbn sbr sbs sia sib sii sin sir sis sna snb sni snn snr sns sr- sra srb sri srn srr srs ss- ssa ssb ssi ssn ssr sss