import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int[] s = new int[6];
        for(int i = 0; i < 6; i++)
            s[i] = in.nextInt();

        Arrays.sort(s);

        int sum = 0;
        for(int i = 1; i < 5; i++)
            sum += s[i];

        System.out.printf("%.2f\n", (double)sum / 4.0);
    }
}