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


public class Main_yukicoder275 {

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

        int n = sc.nextInt();
        int[] a = new int[n];

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

        double ret;
        if (n % 2 != 0) {
        	ret = a[n / 2];
        } else {
        	ret = ((double)a[n / 2] + a[n / 2 - 1]) / 2;
        }
        
        System.out.printf("%.2f\n", ret);

        sc.close();
    }
}