import java.util.*;
import java.io.*;

class Main {
  public static void main(String[] args) throws Exception {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st;
    
    int n = Integer.parseInt(br.readLine());
    int a[] = new int[n];
    st = new StringTokenizer(br.readLine());
    for(int i=0 ; i<n ; i++) {
      a[i] = Integer.parseInt(st.nextToken());
    }
    
    Arrays.sort(a);
    
    double d = a[0];
    for(int i=1 ; i<n ; i++) {
      d = (d*a[i])/2;
    }
    
    System.out.println(d);
  }
}