import java.util.Scanner;

public class Study01 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String a = sc.nextLine();
		String [] q = a.split(" ");
		int[] z = new int[6];
		int max = 0,min = 100;
		for(int i=0;i<q.length;i++){
			z[i]= Integer.parseInt(q[i]);
			//System.out.println(z[i]);
			max = Math.max(max,z[i]);
			min = Math.min(min,z[i]);
		}
		int ll = max + min;
		int all = 0;
		for(int i=0;i<z.length;i++){
			all += z[i];
		}
		double answer = all - ll;
		answer /= 4;
		System.out.println(answer);
	}

}