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

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		float array[] = new float[2 * n - 1];
		for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		}
		Arrays.sort(array);
		System.out.println(array[2 * 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 scan = new Scanner(System.in);
		int n = scan.nextInt();
		float array[] = new float[2 * n - 1];
		for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		}
		Arrays.sort(array);
		System.out.println(array[2 * n - 2]);
	}

} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		float array[] = new float[2 * n - 1];
		for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		}
		Arrays.sort(array);
		System.out.println(array[2 * n - 2]);
	} main {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		float array[] = new float[2 * n - 1];
		for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		}
		Arrays.sort(array);
		System.out.println(array[2 * n - 2]);
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan float array[] = new float[2 * n - 1]; array new float[2 * n - 1] 2 * n - 1 2 * n 2 n 1 for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			array[i] = scan.nextInt();
		} {
			array[i] = scan.nextInt();
		} array[i] = scan.nextInt() array[i] array i scan.nextInt() scan.nextInt scan for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		} int i = 0; int i = 0; i 0 i < n - 1 i n - 1 n 1 i++ i++ i {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		} {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		} Arrays.sort(array) Arrays.sort Arrays array array[i] = (array[n + i - 1] + array[n + i]) / 2 array[i] array i (array[n + i - 1] + array[n + i]) / 2 (array[n + i - 1] + array[n + i]) array[n + i - 1] array n + i - 1 n + i n i 1 array[n + i] array n + i n i 2 array[n+i - 1] = 0 array[n+i - 1] array n+i - 1 n+i n i 1 0 array[n+i] = 0 array[n+i] array n+i n i 0 Arrays.sort(array) Arrays.sort Arrays array System.out.println(array[2 * n - 2]) System.out.println System.out System System.out array[2 * n - 2] array 2 * n - 2 2 * n 2 n 2 String[] args args public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		float array[] = new float[2 * n - 1];
		for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		}
		Arrays.sort(array);
		System.out.println(array[2 * n - 2]);
	}

} public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		float array[] = new float[2 * n - 1];
		for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		}
		Arrays.sort(array);
		System.out.println(array[2 * n - 2]);
	}

} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		float array[] = new float[2 * n - 1];
		for (int i = 0; i < n; i++) {
			array[i] = scan.nextInt();
		}
		for (int i = 0; i < n - 1; i++) {
			Arrays.sort(array);
			array[i] = (array[n + i - 1] + array[n + i]) / 2;
			array[n+i - 1] = 0;
			array[n+i] = 0;
		}
		Arrays.sort(array);
		System.out.println(array[2 * n - 2]);
	}

}