For300-exploit.py

#!/usr/bin/env python2
import binascii
import base64

flag=""
for i in range(0, 20):
    f = open('Chapter' + str(i) + '.zip', 'r')
    content = f.read()
    hex_text = binascii.hexlify(content)
    if int(hex_text[-2:], 16) != 0:
        flag_hex = (hex_text[-16:].rstrip('=')).decode('hex')
        flag += base64.b64decode(flag_hex + '=' * (-len(flag_hex) % 4)).strip('\n')
    f.close()

print flag