Semi-clickbait warning
So it seems to me that some people are complaining about not trying the challenge problem, thus missing a very easy 99 points. I find this very surprising.
“CHALLENGE” Problems are not challenging
The name is misleading, “challenge” problems are just tie-breaker problems that have no intended solution and are scored based on the best solution within the contestants. You can get AC in challenge problems even if you only get 0.1 points.
Because it’s supposed to be a tie-breaker problem, a lot of people should be able to solve it (to break ties between people who score 200 on other problems, for example).
Try all problems
This is part of a bigger problem. Not only should you try the challenge problem, you should try all problems in general.
This is a long challenge, so all problems should be attempted, given the amount of time that people have. Even if you feel like there’s a 99% chance you won’t be able to solve the last problem, still look at it and try it. You may find out that you can get some easy subtask, you may find out that it is similar to another problem you’ve solved before, or you might surprise yourself by being able to solve the problem by yourself.
In any case, you don’t need to actually get any points from a problem to be able to learn from it. Thinking of half of the solution will still be able to improve your problem-solving skills. Also, you get a morale boost when you realize that your solution was in the right direction all along 
Mental Barrier
I read somewhere that a study was conducted, where athletes were told to run as fast as they could in a certain period of time while being videotaped. Sometime later, they were told to match the speed of their previous run. What they didn’t know was that the videos were sped up. And all athletes were able to match the increased speed.
Does it mean that if I created bots to submit a lot of AC solutions to hard problems, more people would be able to solve those hard problems? Perhaps.
Maybe people should try solving problems in long challenges for the first 7 days without looking at the solve counts. Note that in short contests, it’s still better to look at the scoreboard and the solve counts because you need to reduce time penalty and you don’t have a lot of time to think about all problems.
I was going to post this in Weird Bug in Challenge problem but I realized this is important enough and has a lot more stuff to make as a topic alone.
