import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        String str = in.nextLine();
		String[] scores = str.split(" ");
        int sum = 0;
        for(String score : scores){
            sum += Integer.parseInt(score);
        }
        double average = sum / 5.0;
        System.out.printf("%.1f", average);
    }
}