// Page 077 - 078

import java.util.Scanner;
class Prog_6_4
{
	public static void main(String[] args)
	{
			Scanner input = new Scanner(System.in);
			double data;
			int count = 0;
			double sum = 0;
			double average;
			while (input.hasNext())
			{
				data = input.nextDouble();
				sum += data;
				count ++;
			}
			average = sum / count;
			System.out.println("average:"+average);
	}
}