package no394;

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);
		int sum = 0;
		for(int i=1;i<=4;i++) {
			sum += s[i];
		}
		System.out.println(String.format("%.2f", (double) sum / 4));
	}

}