import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws FileNotFoundException {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.next());
		int[] d = new int[N];
		for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(d);
		if(d[N/2-1]==d[N/2]) {
			System.out.println("0");
		} else {
			System.out.println(d[N/2]-d[N/2-1]);
		}
	}
} import java.io.FileNotFoundException; FileNotFoundException java.io import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) throws FileNotFoundException {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.next());
		int[] d = new int[N];
		for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(d);
		if(d[N/2-1]==d[N/2]) {
			System.out.println("0");
		} else {
			System.out.println(d[N/2]-d[N/2-1]);
		}
	}
} Main public static void main(String[] args) throws FileNotFoundException {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.next());
		int[] d = new int[N];
		for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(d);
		if(d[N/2-1]==d[N/2]) {
			System.out.println("0");
		} else {
			System.out.println(d[N/2]-d[N/2-1]);
		}
	} main {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.next());
		int[] d = new int[N];
		for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(d);
		if(d[N/2-1]==d[N/2]) {
			System.out.println("0");
		} else {
			System.out.println(d[N/2]-d[N/2-1]);
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = Integer.parseInt(sc.next()); N Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int[] d = new int[N]; d new int[N] N for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		} int i=0; int i=0; i 0 i<N i N i++ i++ i {
			d[i] = Integer.parseInt(sc.next());
		} {
			d[i] = Integer.parseInt(sc.next());
		} d[i] = Integer.parseInt(sc.next()) d[i] d i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc Arrays.sort(d) Arrays.sort Arrays d 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 String[] args args public class Main {
	public static void main(String[] args) throws FileNotFoundException {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.next());
		int[] d = new int[N];
		for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(d);
		if(d[N/2-1]==d[N/2]) {
			System.out.println("0");
		} else {
			System.out.println(d[N/2]-d[N/2-1]);
		}
	}
} public class Main {
	public static void main(String[] args) throws FileNotFoundException {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.next());
		int[] d = new int[N];
		for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(d);
		if(d[N/2-1]==d[N/2]) {
			System.out.println("0");
		} else {
			System.out.println(d[N/2]-d[N/2-1]);
		}
	}
} Main
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws FileNotFoundException {

		//    	File file = new File("src/in.txt");
		//    	Scanner sc = new Scanner(file);

		Scanner sc = new Scanner(System.in);

		int N = Integer.parseInt(sc.next());
		int[] d = new int[N];
		for(int i=0;i<N;i++) {
			d[i] = Integer.parseInt(sc.next());
		}
		Arrays.sort(d);
		if(d[N/2-1]==d[N/2]) {
			System.out.println("0");
		} else {
			System.out.println(d[N/2]-d[N/2-1]);
		}
	}
}