The binary checks if our input string is correct.
The input string is encoded with base64 and compared with base64-encoded flag.

[writeup](https://ptr-yudai.hatenablog.com/entry/2019/03/25/152043#Reversing-980pts-Warmup-Welcome-to-securinets-CTF)

Original writeup (https://ptr-yudai.hatenablog.com/entry/2019/03/25/152043#Reversing-980pts-Warmup-Welcome-to-securinets-CTF).