text: #!/usr/bin/env python3
  import rospy
  from std_msgs.msg import Int32
  
  n = 1234
  
  def cb(message):
  	global n
  	n = message.data
  
  rospy.init_node('twice')
  sub = rospy.Subscriber('count_up', Int32, cb)
  pub = rospy.Publisher('twice', Int32, queue_size=1)
  rate = rospy.Rate(0.5)
  while not rospy.is_shutdown():
  	pub.publish(n)
  	rate.sleep()
  