import java.util.Arrays;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		double[] v = new double[n];
		double ans = 0;

		for(int i = 0; i< n; i++) {
			v[i] = sc.nextInt();
		}

		Arrays.sort(v);

		ans = (v[0] + v[1])/2;
		for(int i = 2; i < n; i++) {
			ans = (ans + v[i])/2;
		}

		System.out.println(String.format("%.5f", ans));

	}

}