import java.util.*;
import java.util.stream.Stream;
public class No394 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
		int[] s = Stream.of(sc.nextLine().split(" ", 0)).mapToInt(Integer::parseInt).toArray();
		Arrays.sort(s);
		System.out.printf("%.2f", (s[1] + s[2] + s[3] + s[4]) / 4.00);
	}
}