import java.io.*;

public class SinglyMain
{

	public static void main (String [ ] args) 
	{
        	final String SENTINEL = "***";

        	final String PROMPT = "Please enter a GPA (or " + SENTINEL +
					" to quit): ";        

        	final String AVERAGE_MESSAGE = "\n\nThe average GPA is ";

        	SinglyLinkedList<Double> gpaList = new SinglyLinkedList<Double>();

        	BufferedReader reader = new BufferedReader (
						(new InputStreamReader (System.in)));

        	String line;

        	while (true)
        	{
	   		try
	   		{
            			System.out.println (PROMPT);
            			line = reader.readLine ();
            			if (line.equals (SENTINEL))
                			break;
            			gpaList.add (new Double (line));
	    		} // try
	    		catch (IOException e)
	    		{
				System.out.println (e);
	    		} // catch
        	} // while
        	double sum = 0.0;

        	for (Double d : gpaList)
	    		sum += d;
        	System.out.println (AVERAGE_MESSAGE + (sum / gpaList.size ()));
	}  // method main

} // class SinglyMain