import java.text.DecimalFormat;
import java.util.Arrays;
import java.util.Scanner;
public class Yukicoder394 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int[] s = new int[6];
        for (int i = 0; i < 6; i++) {
            s[i] = sc.nextInt();
        }
        Arrays.sort(s);
        System.out.println(new DecimalFormat("0.00").format((s[1] + s[2] + s[3] + s[4])/4.0));
    }
}