a-a a-b aaa aab aae aak aan aao aas ab- aba abb abe abk abn abo abs aea aeb aee aek aen aeo aes aka akb ake akk akn ako aks an- ana anb ane ank ann ano ans aoa aob aoe aok aon aoo aos as- asa asb ase ask asn aso ass baa bab bae bak ban bao bas bba bbb bbe bbk bbn bbo bbs be- bea beb bee bek ben beo bes bka bkb bke bkk bkn bko bks bna bnb bne bnk bnn bno bns boa bob boe bok bon boo bos bsa bsb bse bsk bsn bso bss eaa eab eae eak ean eao eas eba ebb ebe ebk ebn ebo ebs eea eeb eee eek een eeo ees eka ekb eke eko eks en- ena enb ene enk enn eno ens eo- eoa eob eoe eok eon eoo eos es- esa esb ese esk esn eso ess ka- kaa kab kae kak kan kao kas kba kbb kbe kbk kbn kbo kbs ke- kea keb kee kek ken keo kes kkb kke kkk kkn kks kn- kna kne knk knn kno koa kob koe kok kon koo kos ksa ksb kse ksk ksn kso kss naa nab nae nak nan nao nas nba nbb nbe nbk nbn nbo nbs ne- nea neb nee nek nen neo nes nka nke nkk nkn nko nks nna nnb nne nnk nnn nno nns no- noa nob noe nok non noo nos nsa nsb nse nsk nsn nso nss oaa oab oae oak oan oao oas ob- oba obb obe obk obn obo obs oea oeb oee oen oeo oes oka okb oke okk oko oks on- ona onb one onk onn ono ons oo- ooa oob ook oon ooo oos os- osa osb ose osk osn oso oss saa sab sae sak san sao sas sba sbb sbe sbk sbn sbo sbs se- sea seb see sek sen seo ses sk- ska skb ske skk sko sks sna snb sne snk snn sno sns soa sob soe sok son soo sos ss- ssa ssb sse ssk ssn sso sss