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

public class Main {
	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int n = stdIn.nextInt(); //具材
		int [] v = new int[n];
		
		for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		}
		
		Arrays.sort(v);
		
		double [] tmp = new double[n-1];
		
		tmp[0] = (v[0]+v[1])/2.0;
		
		
		for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		}
		System.out.println(tmp[n-2]);
		
	}
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int n = stdIn.nextInt(); //具材
		int [] v = new int[n];
		
		for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		}
		
		Arrays.sort(v);
		
		double [] tmp = new double[n-1];
		
		tmp[0] = (v[0]+v[1])/2.0;
		
		
		for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		}
		System.out.println(tmp[n-2]);
		
	}
} Main public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int n = stdIn.nextInt(); //具材
		int [] v = new int[n];
		
		for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		}
		
		Arrays.sort(v);
		
		double [] tmp = new double[n-1];
		
		tmp[0] = (v[0]+v[1])/2.0;
		
		
		for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		}
		System.out.println(tmp[n-2]);
		
	} main {
		Scanner stdIn = new Scanner(System.in);
		int n = stdIn.nextInt(); //具材
		int [] v = new int[n];
		
		for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		}
		
		Arrays.sort(v);
		
		double [] tmp = new double[n-1];
		
		tmp[0] = (v[0]+v[1])/2.0;
		
		
		for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		}
		System.out.println(tmp[n-2]);
		
	} Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) int n = stdIn.nextInt(); n stdIn.nextInt() stdIn.nextInt stdIn int [] v = new int[n]; v new int[n] n for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			v[i] = stdIn.nextInt();
		} {
			v[i] = stdIn.nextInt();
		} v[i] = stdIn.nextInt() v[i] v i stdIn.nextInt() stdIn.nextInt stdIn Arrays.sort(v) Arrays.sort Arrays v double [] tmp = new double[n-1]; tmp new double[n-1] n-1 n 1 tmp[0] = (v[0]+v[1])/2.0 tmp[0] tmp 0 (v[0]+v[1])/2.0 (v[0]+v[1]) v[0] v 0 v[1] v 1 2.0 for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		} int i = 1; int i = 1; i 1 i < n-1 i n-1 n 1 i++ i++ i {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		} {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		} tmp[i] = (tmp[i-1]+v[i+1])/2 tmp[i] tmp i (tmp[i-1]+v[i+1])/2 (tmp[i-1]+v[i+1]) tmp[i-1] tmp i-1 i 1 v[i+1] v i+1 i 1 2 System.out.println(tmp[n-2]) System.out.println System.out System System.out tmp[n-2] tmp n-2 n 2 String[] args args public class Main {
	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int n = stdIn.nextInt(); //具材
		int [] v = new int[n];
		
		for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		}
		
		Arrays.sort(v);
		
		double [] tmp = new double[n-1];
		
		tmp[0] = (v[0]+v[1])/2.0;
		
		
		for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		}
		System.out.println(tmp[n-2]);
		
	}
} public class Main {
	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int n = stdIn.nextInt(); //具材
		int [] v = new int[n];
		
		for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		}
		
		Arrays.sort(v);
		
		double [] tmp = new double[n-1];
		
		tmp[0] = (v[0]+v[1])/2.0;
		
		
		for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		}
		System.out.println(tmp[n-2]);
		
	}
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int n = stdIn.nextInt(); //具材
		int [] v = new int[n];
		
		for(int i = 0; i < n; i++) {
			v[i] = stdIn.nextInt();
		}
		
		Arrays.sort(v);
		
		double [] tmp = new double[n-1];
		
		tmp[0] = (v[0]+v[1])/2.0;
		
		
		for(int i = 1; i < n-1; i++) {
			tmp[i] = (tmp[i-1]+v[i+1])/2;
		}
		System.out.println(tmp[n-2]);
		
	}
}
