The third round of TCO17 Marathon Competition PoisonedWine started yesterday. It will run for two weeks, and top 30 competitors will get points which then will be converted to t-shirts and trips to the finals (here are the rules). This time the problem was written by timmac, I'm just the tester.
For those interested here is an editorial: https://www.topcoder.com/blog/poisonedwine-marathon-round-solution/