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);
}
}