#include <study.hpp>
 
// Lesson:  Find average of several doubles
// Every exercise will consist of a number of non-negative doubles.  After all
// are read, the stream will become invalid.
 
// Syntax: Check stream state to see if there is more data for this exercise,
// check the lesson to check if there are more exercises.  Lesson created with
// a macro.
 
int main()
{
	START_LESSON(lesson);
	while(lesson) // Will be false after the last exercise
	{
		double d;
		double total = 0.0;
		int count = 0;
		while (study::cin >> d) // Will be true until all data is read.
		{
			total += d;
			++count;
		}
		study::cout << (total/count) << study::endl; // Submits the answer.
	}
}
 

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