a-a a-b a-c aaa aab aac aae aao ab- aba abb abc abe abo ac- aca acb acc ace aco aea aeb aec aee aeo aoa aob aoc aoe aoo baa bab bac bae bao bba bbb bbc bbe bbo bca bcb bcc bce bco be- bea beb bec bee beo boa bob boc boe boo c-- caa cab cac cae cao cba cbb cbc cbe cbo cca ccb ccc cce cco ce- cea ceb cec cee ceo co- coa cob coc coe coo eaa eab eac eae eao eba ebb ebc ebe ebo ec- eca ecb ecc ece eco eea eeb eec eee eeo eo- eoa eob eoc eoe eoo oaa oab oac oae oao ob- oba obb obc obe obo oc- oca ocb occ oco oea oeb oec oee oeo oo- ooa oob ooc ooo