import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
                Scanner in = new Scanner(System.in);
                int a,b,c,d,e;
                a = in.nextInt();
                b = in.nextInt();
                c = in.nextInt();
                d = in.nextInt();
                e = in.nextInt();
                RR rr = new RR();
                double dd = rr.fun(a,b,c,d,e);
                System.out.printf("%.2f",dd);
    }
}
class RR{
  public int fun(int a,int b,int c,int d,int e){ //主类Main中调用RR类，RR类实现计算五个整数平均值
    return (a+b+c+d+e)/5;
  }
}