Hi! I’ve recorded a screencast that includes video solutions for the problems CHEFNWRK (2A), KFOLD (2B), POLYREL (1A/2C), RBTREES (1B/2D), CHEFPRTY (1D), and an idea (which I think is right but may not be; hasn’t been verified) for CHEFHALF (1C/2E). The video is here and there are timestamps for everything in the description. I try to make them as elaborate as possible, but still, feel free to ask questions or leave feedback if something’s unclear. As a note, these are unofficial, and probably differ from the solutions of the real editorials. For example, my solution for CHEFPRTY doesn’t use a segment tree.