I am writing a program that is meant to take user input for a class - Country - and cout the biggest country in terms of area as well as the most densely populated country. I am, however, having with the implementation file. 

What should go into my default constructor? What about other constructors? This is what I have so far:

```
#ifndef COUNTRY_H
#define COUNTRY_H
#include <string>

class Country 
{
public:

   Country(string name, double area, int population);

   Country();

   string get_name () const;

   double get_area()const;

   int get_population()const;

   double population_density(Country popDensity) const;

   void largest_area(double a);

   void largest_population(int p);

   void most_dense(double d);

private:

    string name;
    double area;
    int population;

};

#endif

```

and:

```
#include <iostream>
#include <string>

using namespace std;

#include "COUNTRY_H"

Country :: Country(string name, double area, int population)
{

}

Country :: Country();
{

}

```