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