The nine horizontal and nine vertical lines on an $$8\times8$$ checkerboard form $$r$$ rectangles, of which $$s$$ are squares. The number $$s/r$$ can be written in the form $$m/n,$$ where $$m$$ and $$n$$ are relatively prime positive integers. Find $$m + n.$$

(第十五届AIME1997 第2题)