There is an ancient cypress tree with a sign hanging on the tree, which says: Ask me how old I am this year, 100 is younger than me, 1000 is older than me, each number increases by 2 from left to right, and the sum of the numbers is 21 ． So how old is this tree?
有一株古柏树，树上挂着一块牌子，牌子上写着：要问我今年多少岁，100比我小，1000比我大，从左往右每位数字增加2，各位数字之和是21．那么这棵树有多少岁．
<result>579</result>