Comment by jatari
1 month ago
It's a nice puzzle because at first it seems like you would need to do some complex probability calculations but by just looking at it for a while you can come up with the 1 basic insight that instantly makes the solution obvious.
I still can't find an obvious solution. I think the solution posted by kmm in the top comment is correct, but I still don't think it's obvious. Can you post your solution?