Anyone can help? i made a simple node where it publish Int8 and subsribe to that Int8 but it didnt work

edit

this is the talker and listener i modified . when i compile. it says my std_msgs::Int8 number is not derived from 'const std::istream_iterator..' am i doing something wrong for the variable declaration? i tried int but when i compiled and ran the while(ros::ok()) loop didn't work. the "21!!!!!" did not show up. But it worked fine as in that the listener is subsribed to the talker's topic " chatter" but it was publising the data:21. Anyone have any suggestion or reason as to why i cant use the data or why the programme didn't work?

listener.cpp:

#include "ros/ros.h"
#include "std_msgs/Int8.h"

using namespace std;

void chatterCallback(const std_msgs::Int8::ConstPtr& msg)
{
  // Declare number here
  std_msgs::Int8 number;

  ROS_INFO("I heard: [%d]", msg->data);
  number = msg->data;

  // Check if the number received is 21
  if(number==21)
   {
    ROS_INFO("21!!!!!");
   }
}

int main(int argc, char **argv)
{
  ros::init(argc, argv, "listener");

  ros::NodeHandle n;

  ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);

  ros::spin();

  return 0;
}

talker.cpp:

#include "ros/ros.h"
#include "std_msgs/Int8.h"

#include <sstream>


int main(int argc, char **argv)
{

  ros::init(argc, argv, "talker");


  ros::NodeHandle n;

  ros::Publisher chatter_pub = n.advertise<std_msgs::Int8>("chatter", 1000);

  ros::Rate loop_rate(10);


  int count = 0;
  while (ros::ok())
  {

    std_msgs::Int8 msg;
    msg.data = 21;
    ROS_INFO("%d", msg.data);

    chatter_pub.publish(msg);

    ros::spinOnce();

    loop_rate.sleep();
    ++count;
  }


  return 0;
}