Ask HN: What problem would you propose for a 24h programming contest?

I should propose a problem to be solved in a 24h challenge programming contest for teams with 3 members and it should be in the web area. I would appreciate any kind of problem, no matter if it is web related to not. If it is not, I could rephrase it to have a web related component. I know there are a lot of websites, but I would like to come with something that it is not easy searchable on the web. Thank you