import java.util.*;

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