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 = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(a);
		System.out.println(a[n / 2] - a[n / 2 - 1]);
	}

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

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(a);
		System.out.println(a[n / 2] - a[n / 2 - 1]);
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(a);
		System.out.println(a[n / 2] - a[n / 2 - 1]);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(a);
		System.out.println(a[n / 2] - a[n / 2 - 1]);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int[] a = new int[n]; a new int[n] n for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			a[i] = Integer.parseInt(sc.next());
		} {
			a[i] = Integer.parseInt(sc.next());
		} a[i] = Integer.parseInt(sc.next()) a[i] a i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc Arrays.sort(a) Arrays.sort Arrays a System.out.println(a[n / 2] - a[n / 2 - 1]) System.out.println System.out System System.out a[n / 2] - a[n / 2 - 1] a[n / 2] a n / 2 n 2 a[n / 2 - 1] a n / 2 - 1 n / 2 n 2 1 String[] args args public class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(a);
		System.out.println(a[n / 2] - a[n / 2 - 1]);
	}

} public class Main{

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(a);
		System.out.println(a[n / 2] - a[n / 2 - 1]);
	}

} Main
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 = Integer.parseInt(sc.next());
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(a);
		System.out.println(a[n / 2] - a[n / 2 - 1]);
	}

}
