/* This program is the solution to the problem discussed in the stepwise refineet set of slides.
 * We read in a bunch of test grades, one by one. The user can enter as many as they want, and the stop by entering -1.
 * Here, -1 is a "sentinel value"
 * The problem is to calculate the average of the test grades.
 */
#include<iostream>

using namespace std;

int main()
{
	//declare the variables required first
	double grade;
	double sum=0;
	int count=0;

	double avg;

	//We have to get at least one value from the user.
	// A do-while loop makes sense here
	do
	{
		cout<<"Enter the grade. (-1 to stop): ";
		cin>>grade;
		
		//We only need to count the entry as a grade if it is not -1
		if(grade != -1)
		{
			sum = sum+ grade;
			count = count +1; //We need a count for the average
		}
	}while(grade != -1); //Stop if we have -1

	if(count!=0) //To avoid dividing by 0 and breaking physics
	{	
		avg= sum/count;
		cout<<"The test average is "<<avg<<endl;
	}
	else cout<<"No students in the class."<<endl;

	return 0;
}