Communication between node and topic

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Hi! I have this rqt_graph: rqt.png I wish /cmd_vel topic writes values on /mavros node. The node on which I work is mavros_node.cpp. Initially it was so:

#include <mavros/mavros.h>

int main(int argc, char *argv[])
{
ros::init(argc, argv, "mavros");

mavros::MavRos mavros;
mavros.spin();

return 0;
}

Now I have modified it for my case as well:

#include <mavros/mavros.h>
#include <geometry_msgs/TwistStamped.h>

int main(int argc, char **argv)
{
ros::init(argc, argv, "mavros");
ros::NodeHandle n;
ros::Subscriber mav_sub = n.subscribe<geometry_msgs::TwistStamped>("/cmd_vel", 10);
ros::Rate loop_rate(10);
mavros::MavRos mavros;
mavros.spin();

return 0;
}

but I can not fill with catkin_make because errors there are. Can anyone help me? Thanks in advance.