import java.util.Arrays;
import java.util.Scanner;

public class Main {

	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);
		double ans = s[1] + s[2] + s[3] + s[4];
		System.out.printf("%.2f\n", ans / 4.0);
	}
}