For a better view check our [githubpage](https://bsempir0x65.github.io/CTF_Writeups/SEETF_CTF_2022/#regex101) or [github](https://github.com/bsempir0x65/CTF_Writeups/tree/main/SEETF_CTF_2022#regex101) out
![regex101](https://raw.githubusercontent.com/bsempir0x65/CTF_Writeups/main/SEETF_CTF_2022/img/regex101.png)
This was actually one of the challenges which did not really have something to do with hacking. This was more or less a training task to recognize that being able to use regex expressions can be crucial. Based on the name of the challenge we thought this was a hint to use the site [regex101](https://regex101.com/) so that's what we did. So we "cat" the attached file to have all 2999 and copied them into regex101.
 ![regex101](https://raw.githubusercontent.com/bsempir0x65/CTF_Writeups/main/SEETF_CTF_2022/img/regex101_1.png)
As you can see in the Screenshot we already have only one match with the regex \[A-Z\]\{5\}\[1-9\]\{5\}\[A-Z\]\{6\} which brings us the flag SEE{RGSXG13841KLWIUO}. On the right side you also have a nice explanation why this regex matches and what the single parts do. Play around a bit with it and use the references or the regex quiz on the left side to improve your regex skills.