import sys

file1_b = bytearray(open(sys.argv[1], 'rb').read())
file2_b = bytearray(open(sys.argv[2], 'rb').read())

size = len(file1_b) if file1_b < file2_b else len(file2_b)
xored = bytearray(size)

for i in range(size):
    xored = file1_b[i] ^ file2_b[i]

open(sys.argv[3], 'wb').write(xord_byte_array)