a-a a-b a-c aaa aab aac aae aao aas ab- aba abb abc abe abo abs ac- aca acb acc ace aco acs aea aeb aec aee aeo aes aoa aob aoc aoe aoo aos as- asa asb asc ase aso ass baa bab bac bae bao bas bba bbb bbc bbe bbo bbs bca bcb bcc bce bco bcs be- bea beb bec bee beo bes boa bob boc boe boo bos bsa bsb bsc bse bso bss c-- caa cab cac cae cao cas cba cbb cbc cbe cbo cbs cca ccb ccc cce cco ccs ce- cea ceb cec cee ceo ces co- coa cob coc coe coo cos csa csb csc cse cso css eaa eab eac eae eao eas eba ebb ebc ebe ebo ebs ec- eca ecb ecc ece eco ecs eea eeb eec eee eeo ees eo- eoa eob eoc eoe eoo eos es- esa esb esc ese eso ess oaa oab oac oae oao oas ob- oba obb obc obe obo obs oc- oca ocb occ oco ocs oea oeb oec oee oeo oes oo- ooa oob ooc ooo oos os- osa osb osc ose oso oss saa sab sac sae sao sas sba sbb sbc sbe sbo sbs sca scb scc sce sco scs se- sea seb sec see seo ses soa sob soc soe soo sos ss- ssa ssb ssc sse sso sss