import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] f = new double[N];
		for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble();
		Arrays.sort(f);
		double[] nf = new double[N - 1];
		nf[0] = (f[0] + f[1]) / 2;
		for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		}
		System.out.println(String.format("%.5f", nf[nf.length - 1]));
		sc.close();
	}
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] f = new double[N];
		for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble();
		Arrays.sort(f);
		double[] nf = new double[N - 1];
		nf[0] = (f[0] + f[1]) / 2;
		for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		}
		System.out.println(String.format("%.5f", nf[nf.length - 1]));
		sc.close();
	}
} Main public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] f = new double[N];
		for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble();
		Arrays.sort(f);
		double[] nf = new double[N - 1];
		nf[0] = (f[0] + f[1]) / 2;
		for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		}
		System.out.println(String.format("%.5f", nf[nf.length - 1]));
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] f = new double[N];
		for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble();
		Arrays.sort(f);
		double[] nf = new double[N - 1];
		nf[0] = (f[0] + f[1]) / 2;
		for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		}
		System.out.println(String.format("%.5f", nf[nf.length - 1]));
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc double[] f = new double[N]; f new double[N] N for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble(); int i = 0; int i = 0; i 0 i < f.length i f.length f f.length i++ i++ i f[i] = sc.nextDouble(); f[i] = sc.nextDouble() f[i] f i sc.nextDouble() sc.nextDouble sc Arrays.sort(f) Arrays.sort Arrays f double[] nf = new double[N - 1]; nf new double[N - 1] N - 1 N 1 nf[0] = (f[0] + f[1]) / 2 nf[0] nf 0 (f[0] + f[1]) / 2 (f[0] + f[1]) f[0] f 0 f[1] f 1 2 for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		} int i = 2; int i = 2; i 2 i < f.length i f.length f f.length i++ i++ i {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		} {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		} nf[i - 1] = (nf[i - 2] + f[i]) / 2 nf[i - 1] nf i - 1 i 1 (nf[i - 2] + f[i]) / 2 (nf[i - 2] + f[i]) nf[i - 2] nf i - 2 i 2 f[i] f i 2 System.out.println(String.format("%.5f", nf[nf.length - 1])) System.out.println System.out System System.out String.format("%.5f", nf[nf.length - 1]) String.format String "%.5f" nf[nf.length - 1] nf nf.length - 1 nf.length nf nf.length 1 sc.close() sc.close sc String[] args args public class Main {

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] f = new double[N];
		for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble();
		Arrays.sort(f);
		double[] nf = new double[N - 1];
		nf[0] = (f[0] + f[1]) / 2;
		for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		}
		System.out.println(String.format("%.5f", nf[nf.length - 1]));
		sc.close();
	}
} public class Main {

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] f = new double[N];
		for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble();
		Arrays.sort(f);
		double[] nf = new double[N - 1];
		nf[0] = (f[0] + f[1]) / 2;
		for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		}
		System.out.println(String.format("%.5f", nf[nf.length - 1]));
		sc.close();
	}
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] f = new double[N];
		for (int i = 0; i < f.length; i++)
			f[i] = sc.nextDouble();
		Arrays.sort(f);
		double[] nf = new double[N - 1];
		nf[0] = (f[0] + f[1]) / 2;
		for (int i = 2; i < f.length; i++) {
			nf[i - 1] = (nf[i - 2] + f[i]) / 2;
		}
		System.out.println(String.format("%.5f", nf[nf.length - 1]));
		sc.close();
	}
}