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[] d = new int[n];
		for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		if(d.length % 2 == 1) {
			System.out.println(0);
		}
		int hanbun = d.length / 2;
		System.out.println(d[hanbun] - d[hanbun - 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 = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		if(d.length % 2 == 1) {
			System.out.println(0);
		}
		int hanbun = d.length / 2;
		System.out.println(d[hanbun] - d[hanbun - 1]);
	}
} Main public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		if(d.length % 2 == 1) {
			System.out.println(0);
		}
		int hanbun = d.length / 2;
		System.out.println(d[hanbun] - d[hanbun - 1]);
	} main {

		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		if(d.length % 2 == 1) {
			System.out.println(0);
		}
		int hanbun = d.length / 2;
		System.out.println(d[hanbun] - d[hanbun - 1]);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] d = new int[n]; d new int[n] n for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		} int i = 0 ; int i = 0 ; i 0 i < n i n i++ i++ i {
			d[i] = sc.nextInt();
		} {
			d[i] = sc.nextInt();
		} d[i] = sc.nextInt() d[i] d i sc.nextInt() sc.nextInt sc Arrays.sort(d) Arrays.sort Arrays d if(d.length % 2 == 1) {
			System.out.println(0);
		} d.length % 2 == 1 d.length % 2 d.length d d.length 2 1 {
			System.out.println(0);
		} System.out.println(0) System.out.println System.out System System.out 0 int hanbun = d.length / 2; hanbun d.length / 2 d.length d d.length 2 System.out.println(d[hanbun] - d[hanbun - 1]) System.out.println System.out System System.out d[hanbun] - d[hanbun - 1] d[hanbun] d hanbun d[hanbun - 1] d hanbun - 1 hanbun 1 String[] args args public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		if(d.length % 2 == 1) {
			System.out.println(0);
		}
		int hanbun = d.length / 2;
		System.out.println(d[hanbun] - d[hanbun - 1]);
	}
} public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		if(d.length % 2 == 1) {
			System.out.println(0);
		}
		int hanbun = d.length / 2;
		System.out.println(d[hanbun] - d[hanbun - 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 = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0 ; i < n ; i++) {
			d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		if(d.length % 2 == 1) {
			System.out.println(0);
		}
		int hanbun = d.length / 2;
		System.out.println(d[hanbun] - d[hanbun - 1]);
	}
}

