cidr

#!/usr/bin/env python3
#
# CIDR calculator: find the minimum CIDR which contains multiple ip addresses
#
# Example:
#   $ cidr 142.250.66.78 142.250.204.142 142.251.130.14
#   142.250.0.0/15
#

import os
import sys

comm = os.path.commonprefix(['.'.join(['{:08b}'.format(int(i)) for i in ip.split('.')]) for ip in sys.argv[1:]]).rstrip('.')
addr = '.'.join(([str(int('{:0<8s}'.format(i), 2)) for i in comm.split('.')] + ['0']*4)[:4])
bits = sum(len(i) for i in comm.split('.'))
cidr = '{}/{}'.format(addr, bits)
print(cidr)