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 = sc.nextInt();
		int a[] = new int[n];
		for (int i = 0; i <= n - 1; i++) {
			a[i] = sc.nextInt();
		}
	Arrays.sort(a);

	int me=-1+n/2;

System.out.println(a[me+1]-a[me]);
	}} 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 = sc.nextInt();
		int a[] = new int[n];
		for (int i = 0; i <= n - 1; i++) {
			a[i] = sc.nextInt();
		}
	Arrays.sort(a);

	int me=-1+n/2;

System.out.println(a[me+1]-a[me]);
	}} Main 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 - 1; i++) {
			a[i] = sc.nextInt();
		}
	Arrays.sort(a);

	int me=-1+n/2;

System.out.println(a[me+1]-a[me]);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int a[] = new int[n];
		for (int i = 0; i <= n - 1; i++) {
			a[i] = sc.nextInt();
		}
	Arrays.sort(a);

	int me=-1+n/2;

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

	int me=-1+n/2;

System.out.println(a[me+1]-a[me]);
	}} public class Main {
	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 - 1; i++) {
			a[i] = sc.nextInt();
		}
	Arrays.sort(a);

	int me=-1+n/2;

System.out.println(a[me+1]-a[me]);
	}} 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 = sc.nextInt();
		int a[] = new int[n];
		for (int i = 0; i <= n - 1; i++) {
			a[i] = sc.nextInt();
		}
	Arrays.sort(a);

	int me=-1+n/2;

System.out.println(a[me+1]-a[me]);
	}}