In this challenge you will be asked to insert a file extension for the given binary part of a file. You must correctly answer for all questions and then the flag occuers. Some files can be identificated by `file` utility, but I've also used google and guessing.
One of the interesting file:
```
b'652076206c207a207b207320302075206e2064205f20302066'
```
If you decode it, it looks like a part of the flag, but it is not :)

Python code:
```
from pwn import *

try:
r = remote('35.198.113.131', 60000)
print r.recvuntil("\n")
print r.recvuntil("\n")

while True:
f = r.recvuntil("\n")
print f

if 'WEBP' in f:
print 'WEBP'
r.sendline('WEBP')
elif '[Content_Types].xml' in f:
print 'DOCX'
r.sendline('DOCX')
elif '#!/bin/bash\\nsudo' in f:
print 'SH'
r.sendline('SH')
elif 'BM|' in f:
print 'BMP'
r.sendline('BMP')
elif 'Date: Sun,' in f:
print 'EML'
r.sendline('EML')
elif 'PNG' in f:
print 'PNG'
r.sendline('PNG')
elif b'%PDF-1.6' in f:
print 'PDF'
r.sendline('PDF')
elif 'KDMV' in f:
print 'VMDK'
r.sendline('VMDK')
elif 'debian' in f:
print 'DEB'
r.sendline('DEB')
elif '#include' in f:
print 'C'
r.sendline('C')
elif 'matroskaB' in f:
print 'MKV'
r.sendline('MKV')
elif 'GIF89' in f:
print 'GIF'
r.sendline('GIF')
elif 'gimp' in f:
print 'XCF'
r.sendline('XCF')
elif 'ELF' in f:
print 'ELF'
r.sendline('ELF')
elif 'ID3' in f:
print 'MP3'
r.sendline('MP3')
elif '7z\\xbc\\xaf' in f:
print '7Z'
r.sendline('7Z')
elif 'CWS' in f:
print 'SWF'
r.sendline('SWF')
elif 'announce' in f:
print 'TORRENT'
r.sendline('TORRENT')
elif 'flag.txt4' in f:
print 'ZIP'
r.sendline('ZIP')
elif 'SQLite' in f:
print 'DB'
r.sendline('DB')
elif '3gp4' in f:
print '3GP'
r.sendline('3GP')
elif '\\x1f\\x8b\\x08\\x00\\x00\\x00\\x00' in f:
print 'GZ'
r.sendline('GZ')
elif b'\\x00\\x00\\x01\\x00\\x07\\x00\\x00\\x00' in f:
print 'ICO'
r.sendline('ICO')
elif 'JFIF' in f:
print 'JPG'
r.sendline('JPG')
elif '\\xd4\\xc3\\xb2\\xa1\\x02\\x00\\x04\\x00' in f:
print 'PCAP'
r.sendline('PCAP')
elif '\\xff\\xfe\\r\\x00\\n\\x00' in f:
print 'INI'
r.sendline('INI')
elif '\\xebc\\x90\\xd0\\xbc\\x00' in f:
print 'BIN'
r.sendline('BIN')
elif '\\xed\\xab\\xee\\xdb\\x03\\x00' in f:
print 'RPM'
r.sendline('RPM')
elif 'IDA1' in f:
print 'IDB'
r.sendline('IDB')
elif '652076206c207a207b20' in f:
print 'TXT'
r.sendline('TXT')
elif "version: '3'" in f:
print 'YML'
r.sendline('YML')
else:
print f
break

r.interactive()
except:
raise
```

The flag:
```
evlz{thanos_tapped_you_back_in}ctf
```