please any solve this 1.#QNAN error in the output

[rahmed17]

#include<iostream>
using namespace std;

class Planet
{
	protected:
		string Name;
		double Radius;
		double Distance;
	public:
		Planet(string _name, double _radius, double _distance)
		{
			Name = _name;
			Radius = _radius;
			Distance = _distance;
		}
		void Print()
		{
			cout << "Name of Planet is = " << Name << endl;
			cout << "Radius of Planet is " << Radius << endl;
			cout << "Distance of Planet from SUN in AU is " << Distance << endl;
		}
		double Cal_Distance()
		{
			cout << "Planet's Calculate Distance Function is Called"<< endl;
			return( Distance * 15000000 );
		}
};

class Inner_Planet : Planet
{
	
	public:
		Inner_Planet(string _name, double _radius, double _distance)
		: Planet(_name, _radius, _distance)
		{

		}
		void Print()
		{
			Planet::Print();
		}
		double Cal_Distance()
		{
			cout << "Inner Planet's Calculate Distance Function is Called"<< endl;
			Planet::Cal_Distance();
		}
};
class Mercury : Inner_Planet
{
	public:
		Mercury(string _name, double _radius, double _distance)
			: Inner_Planet(_name, _radius, _distance)
		{

		}
		void Print()
		{
			Inner_Planet::Print();
		}
		double Cal_Distance()
		{
			cout << "Mercury's Calculate Distance Function is Called"<< endl;
			Inner_Planet::Cal_Distance();
		}
};
int main()
{
	double result;
	Mercury m("Mercury", 2440, 0.38);
	cout << endl;
	cout << "********** Values of Data Members *********" << endl;
	m.Print();
	cout << endl;
	cout << endl;
	cout << "-================================" << endl<< endl<< endl;
	cout << "******** Calculating Distance of Mercury from SUN in Kilometers ***********" << endl;
	result = m.Cal_Distance();
	cout << "Distance of Mercury From Sun in Kilometers is     " << result << endl << endl;
	system("pause");
}

[2kaud]

in the derived classes, Cal_distance() needs to return a value. So

double Cal_Distance()
		{
			cout << "Inner Planet's Calculate Distance Function is Called"<< endl;
			return Planet::Cal_Distance();
		}
...
double Cal_Distance()
		{
			cout << "Mercury's Calculate Distance Function is Called"<< endl;
			return Inner_Planet::Cal_Distance();
		}

[rahmed17]

in the derived classes, Cal_distance() needs to return a value. So

double Cal_Distance()
		{
			cout << "Inner Planet's Calculate Distance Function is Called"<< endl;
			return Planet::Cal_Distance();
		}
...
double Cal_Distance()
		{
			cout << "Mercury's Calculate Distance Function is Called"<< endl;
			return Inner_Planet::Cal_Distance();
		}

Thnx for recitify my code