a-a a-b aaa aab aad aae aak aas ab- aba abb abd abe abk abs ad- ada adb add ade adk ads aea aeb aed aee aek aes aka akb akd ake akk aks as- asa asb asd ase ask ass baa bab bad bae bak bas bba bbb bbd bbe bbk bbs bda bdb bdd bde bdk bds be- bea beb bed bee bek bes bka bkb bke bkk bks bsa bsb bsd bse bsk bss daa dab dad dae dak das dba dbb dbd dbe dbk dbs dda ddb ddd dde ddk dds de- dea deb ded dee dek des dka dkb dke dkk dks dsa dsb dsd dse dsk dss eaa eab ead eae eak eas eba ebb ebd ebe ebk ebs ed- eda edb edd ede edk eds eea eeb eed eee eek ees eka ekb ekd eke eks es- esa esb esd ese esk ess ka- kaa kab kad kae kak kas kba kbb kbd kbe kbk kbs kda kdb kde kdk kds ke- kea keb ked kee kek kes kkb kke kkk kks ksa ksb ksd kse ksk kss saa sab sad sae sak sas sba sbb sbd sbe sbk sbs sda sdb sdd sde sdk sds se- sea seb sed see sek ses sk- ska skb skd ske skk sks ss- ssa ssb ssd sse ssk sss