Implementing a subscriber with std_msgs::Int16

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Hello. I am new to ros and rosserial in general. After going through the beginner tutorials on rosserial-arduino, I decided to modify the blink example that comes with the ros library so that whenever I enter the following in the terminal:

rosoptic pub Led_Brigghtness std_msgs/Int16 x (where x is between 0 and 100)

it maps it into the range of arduino analog values and then changes the brightness of the led. However, I am having problems in declaring a suitable subscriber. I was previously about to create a custom message for this but after I discovered that std_msgs has int data types, I figured I could use those instead. I have the following code:

#include <ros.h>
#include <std_msgs/Int16.h>

ros::NodeHandle  nh;
int Control_Pin = 3;
std_msgs::Int16 User_Input;

void messageCb( std_msgs::Int16 & Brightness){
  int brightness = map(User_Input.data, 0, 100, 0, 254);
  analogWrite(Control_Pin, brightness);   // blink the led
}

ros::Subscriber<std_msgs::Int16> sub("Led_Brightness", &User_Input);

void setup()
{ 
  pinMode(Control_Pin, OUTPUT);
  nh.initNode();
  nh.subscribe(sub);
}

void loop()
{  
  nh.spinOnce();
  delay(1);
}

When I try to compile the code, I get an error on the segment:

ros::Subscriber<std_msgs::Int16> sub("Led_Brightness", &User_Input);

that says:

no matching function for call to 'ros::Subscriber<std_msgs::Int16>::Subscriber(const char [15], std_msgs::Int16*)