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)