Hello, Codeforces! I made announces of rounds quite often, so some time ago I made a script that gives out the entire list of testers divided by colors. Of course, you can rewrite it a little, so that the order is whatever you want.
Script uses Codeforces API, so first of all you need to go to your account settings and generate API keys and put the open one in the "key" file, and the secret one in the "secret" file in the same folder with the script (or just assign them to the corresponding variables in the script). Now you just need to fill in the array contestids with ids of mashups that you used for testing and run the script. At the end of its work, the script will create file "en.txt " with thanks to all the testers.
I hope it will help you to quickly change the list of testers. Good luck to all and successful rounds!
