import java.util.*;
import java.math.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		int[] ar = new int[6];
		for (int i=0; i<6; i++) {
			ar[i] = sc.nextInt();
		}
		Arrays.sort(ar);
		double total = 0;
		for (int i=1; i<5; i++) {
			total += ar[i];
		}
		
		BigDecimal bd1 = BigDecimal.valueOf(total);
		BigDecimal bd2 = BigDecimal.valueOf(4);
		BigDecimal bd3 = bd1.divide(bd2,3,RoundingMode.HALF_UP);
		System.out.println(bd3);
	}
}