import java.util.*;

public class pre {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
		int judge[] = new int[6];
		
		for(int i=0;i<6;i++){
			judge[i] = s.nextInt();
		}
		
		Arrays.sort(judge);
		
		System.out.printf("%.2f\n",(double)(judge[1] + judge[2] + judge[3] + judge[4]) / 4.0);
    }
}