This question sounded familiar, and in fact it's a special case or the Erdos-Szekeres theorem (1935): < http://en.wikipedia.org/wiki/Erdős–Szekeres_theorem >, original paper at < http://archive.numdam.org/ARCHIVE/CM/CM_1935__2_/CM_1935__2__463_0/CM_1935__... >. The theorem states that any set of integers of size (r-1)(s-1) + 1 has either an increasing subsequence of size r or an increasing subsequence of length s. --Dan ________________________________________________________________________________________ "Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read." --Groucho Marx