import java.util.Scanner;


import java.util.Comparator;
import java.util.Arrays;
import java.util.ArrayList;



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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-1] );
		}
	}
} import java.util.Scanner; Scanner java.util import java.util.Comparator; Comparator java.util import java.util.Arrays; Arrays java.util import java.util.ArrayList; ArrayList 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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-1] );
		} n%2 == 1 n%2 n 2 1 {
			System.out.println(0);
		} System.out.println(0) System.out.println System.out System System.out 0 {
			int half = n/2;
			System.out.println(d[half] - d[half-1] );
		} int half = n/2; half n/2 n 2 System.out.println(d[half] - d[half-1] ) System.out.println System.out System System.out d[half] - d[half-1] d[half] d half d[half-1] d half-1 half 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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-1] );
		}
	}
} Main
import java.util.Scanner;


import java.util.Comparator;
import java.util.Arrays;
import java.util.ArrayList;



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(n%2 == 1) {
			System.out.println(0);
		}
		else {
			int half = n/2;
			System.out.println(d[half] - d[half-1] );
		}
	}
}
