a-a a-b a-c aaa aab aac aae aak aas ab- aba abb abc abe abk abs ac- aca acb acc ace ack acs aea aeb aec aee aek aes aka akb akc ake akk aks as- asa asb asc ase ask ass baa bab bac bae bak bas bba bbb bbc bbe bbk bbs bca bcb bcc bce bck bcs be- bea beb bec bee bek bes bka bkb bkc bke bkk bks bsa bsb bsc bse bsk bss c-- caa cab cac cae cak cas cba cbb cbc cbe cbk cbs cca ccb ccc cce cck ccs ce- cea ceb cec cee cek ces cka ckb ckc cks csa csb csc cse csk css eaa eab eac eae eak eas eba ebb ebc ebe ebk ebs ec- eca ecb ecc ece eck ecs eea eeb eec eee eek ees eka ekb ekc eke eks es- esa esb esc ese esk ess ka- kaa kab kac kae kak kas kba kbb kbc kbe kbk kbs kca kcb kcc kce kck kcs ke- kea keb kec kee kek kes kkb kkc kke kkk kks ksa ksb ksc kse ksk kss saa sab sac sae sak sas sba sbb sbc sbe sbk sbs sca scb scc sce sck scs se- sea seb sec see sek ses sk- ska skb skc ske skk sks ss- ssa ssb ssc sse ssk sss