Firstly I thought it was only some bug with the server and the administrator would fix it soon. But later I discovered that it seemed to be a new change to this website. Why Codeforces doesn't provide data now? I think it's a very nice function for users to find their mistakes and correct them. Otherwise we would take lots of time to read the code or use random data to find our mistakes, which is obviously a long-time job and can't ensure us to finish it. Among all the code websites I use, only Codeforces provide data, and that's why I like to use it as training. But now everything changed. Could you please explain why you do this? Thanks!