What a neat problem. I hadn't seen this before. You don't need quite that many -- you could test 2^289 (and you can probably skip many of them) and look for th

What a neat problem. I hadn't seen this before. You don't need quite that many -- you could test 2^289 (and you can probably skip many of them) and look for the "rectangle free subsets" that he mentions in the slides, and then just look for four of them that don't overlap. Still gonna take eons.