import java.util.*;

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 < 5; i++) {
      sum += s[i];
    }
    String ans = String.valueOf(sum / 4);
    if(sum % 4 == 1) {
      ans += ".25";
    } else if(sum % 4 == 2) {
      ans += ".50";
    } else if(sum % 4 == 3) {
      ans += ".75";
    } else {
      ans += ".00";
    }
    System.out.println(ans);
  }
}