a-a a-b aaa aab aae aan aao aas ab- aba abb abe abn abo abs aea aeb aee aen aeo aes an- ana anb ane ann ano ans aoa aob aoe aon aoo aos as- asa asb ase asn aso ass baa bab bae ban bao bas bba bbb bbe bbn bbo bbs be- bea beb bee ben beo bes bna bnb bne bnn bno bns boa bob boe bon boo bos bsa bsb bse bsn bso bss eaa eab eae ean eao eas eba ebb ebe ebn ebo ebs eea eeb eee een eeo ees en- ena enb ene enn eno ens eo- eoa eob eoe eon eoo eos es- esa esb ese esn eso ess naa nab nae nan nao nas nba nbb nbe nbn nbo nbs ne- nea neb nee nen neo nes nna nnb nne nnn nno nns no- noa nob noe non noo nos nsa nsb nse nsn nso nss oaa oab oae oan oao oas ob- oba obb obe obn obo obs oea oeb oee oen oeo oes on- ona onb one onn ono ons oo- ooa oob oon ooo oos os- osa osb ose osn oso oss saa sab sae san sao sas sba sbb sbe sbn sbo sbs se- sea seb see sen seo ses sna snb sne snn sno sns soa sob soe son soo sos ss- ssa ssb sse ssn sso sss