new_contents: #!/usr/bin/env python
  import rospy
  from std_msgs.msg import Int32
  
  n = 0
  
  def cb(message):
      global n
      n = message.data*3
  
  if __name__ == '__main__':
      rospy.init_node('third')
      sub = rospy.Subscriber('count_up', Int32, cb)
      pub = rospy.Publisher('third', Int32, queue_size=1)
      rate = rospy.Rate(10)
      while not rospy.is_shutdown():
          pub.publish(n)
          rate.sleep()
  
subject: Create third.py