Recently, I've seen a lot of blogs talking about the issues of cheaters. So, I make up a problem about using automatic system to catch them.

Currently, the most well-known automatic system for assisting of detecting plagiarism is MOSS(from Stanford). At first, I asked myself, why didn't Codeforces use them? However, I look at the number of participants of each contests; it turns out that the count is approximately under 30000. So, we have to compare $$$4.5*10^8$$$