solve.py

from base64 import b64decode
MASKS = """
192.168.55.86/255.255.255.0
192.168.80.198/255.255.255.128
192.168.1.228/255.255.255.128
192.168.90.68/255.255.254.0
192.168.8.214/255.255.255.128
192.168.5.197/255.255.255.128
192.168.71.90/255.255.255.0
192.168.62.55/255.255.255.192
192.168.78.209/255.255.255.128
192.168.76.216/255.255.255.128
192.168.91.202/255.255.255.128
192.168.93.108/255.255.255.0
192.168.74.76/255.255.254.0
192.168.10.88/255.255.254.0
192.168.82.236/255.255.255.128
192.168.13.246/255.255.255.128
192.168.99.228/255.255.255.128
192.168.68.83/255.255.252.0
192.168.23.113/255.255.255.192
192.168.52.113/255.255.255.192
192.168.69.99/255.255.255.0
192.168.19.114/255.255.255.192
192.168.53.236/255.255.255.128
192.168.90.117/255.255.254.0
192.168.35.90/255.255.255.0
192.168.91.121/255.255.255.0
192.168.48.49/255.255.255.192
192.168.27.104/255.255.255.0
192.168.98.204/255.255.255.128
192.168.93.87/255.255.255.0
192.168.44.113/255.255.255.192
192.168.40.104/255.255.248.0
192.168.25.227/255.255.255.128
192.168.57.50/255.255.255.192
192.168.97.115/255.255.255.0
192.168.30.47/255.255.255.192
192.168.10.102/255.255.254.0
192.168.51.209/255.255.255.128
192.168.82.125/255.255.255.192
192.168.72.125/255.255.255.192
""".strip().split()

flag = ''
for mask in MASKS:
    addr, mask = [map(int, x.split('.')) for x in mask.split('/')]
    result = [a & ~b for a, b in zip(addr, mask)]
    flag += chr(result[-1])
print(b64decode(flag))
# b'TWCTF{Are-you-using-a-mask?}'