new_contents: import base64
  
  def fixed_xor(hex_a, hex_b):
      decoded_a = base64.b16decode(hex_a, True)
      decoded_b = base64.b16decode(hex_b, True)
      xor_result = [chr(ord(a) ^ ord(b)) for a, b in zip(decoded_a, decoded_b)]
  
      return base64.b16encode(''.join(xor_result))
  
  if __name__ == '__main__':
      hex_a = raw_input("hex_a> ")
      hex_b = raw_input("hex_b> ")
  
      print fixed_xor(hex_a, hex_b)
  
subject: Add solution to challenge 2.