As it turns out, after a few hours, the elves started to realize themselves that there were other more important things they should be doing than holding parties, so fortunately you didn't have to stop all the parties yourself. They've mostly gone to a building with a grid of windows, and they apparently think the windows of the building are a puzzle of some sort?
The elves have written down which windows are lit, representing an unlit window by . and a lit window by #; they want you to look at which floors have no lit windows, and convert the result from binary, reading from top to bottom (no lit windows = 1, any lit windows = 0).