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

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		}

		sc.close();

	}

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

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		}

		sc.close();

	}

} Main public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		}

		sc.close();

	} main {
		// TODO 自動生成されたメソッド・スタブ
		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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		}

		sc.close();

	} 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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		} n%2 != 0 n%2 n 2 0 {
			System.out.println(0);
		} System.out.println(0) System.out.println System.out System System.out 0 {
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		} if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			} d[(n/2)-1]==d[n/2] d[(n/2)-1] d (n/2)-1 (n/2) n 2 1 d[n/2] d n/2 n 2 {
				System.out.println(0);
			} System.out.println(0) System.out.println System.out System System.out 0 {
				System.out.println(d[n/2]-d[(n/2)-1]);
			} System.out.println(d[n/2]-d[(n/2)-1]) System.out.println System.out System System.out d[n/2]-d[(n/2)-1] d[n/2] d n/2 n 2 d[(n/2)-1] d (n/2)-1 (n/2) n 2 1 sc.close() sc.close sc String[] args args public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		}

		sc.close();

	}

} public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		}

		sc.close();

	}

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

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		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(n%2 != 0){
			System.out.println(0);
		}else{
			if(d[(n/2)-1]==d[n/2]){
				System.out.println(0);
			}else{
				System.out.println(d[n/2]-d[(n/2)-1]);
			}
		}

		sc.close();

	}

}
