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

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

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

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

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

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

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

}