Using the Codeforces API (https://codeforces.com/apiHelp), we will create a list of contests "SuperJ6" participated in and create a list of users who participated in these contests. Afterwards, we will go through all the contests "SuperJ6" did not participate in, find participants who is not in the previous list, and try to identify the secondary account from there.
The script.py will do this for us and return the top 10 accounts that participated the most in the contests "SuperJ6" didn't participate, while never participating in any of the contests "SuperJ6" participated. Testing out each of the accounts as a flag, we find that "MaddyBeltran" works.
Flag: LITCTF{MaddyBeltran}