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

public class Main {
	public static void main(String arg[]) {

		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);

		System.out.print(d[N / 2] - d[N / 2 - 1]);
	}
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String arg[]) {

		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);

		System.out.print(d[N / 2] - d[N / 2 - 1]);
	}
} Main public static void main(String arg[]) {

		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);

		System.out.print(d[N / 2] - d[N / 2 - 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);

		System.out.print(d[N / 2] - d[N / 2 - 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 System.out.print(d[N / 2] - d[N / 2 - 1]) System.out.print 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 arg[] arg public class Main {
	public static void main(String arg[]) {

		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);

		System.out.print(d[N / 2] - d[N / 2 - 1]);
	}
} public class Main {
	public static void main(String arg[]) {

		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);

		System.out.print(d[N / 2] - d[N / 2 - 1]);
	}
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String arg[]) {

		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);

		System.out.print(d[N / 2] - d[N / 2 - 1]);
	}
}