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[] a = new int[(int) n];
		for (int i=0; i<n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		System.out.println(a[n/2] - a[n/2-1]);
		sc.close();
	}

} 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[] a = new int[(int) n];
		for (int i=0; i<n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		System.out.println(a[n/2] - a[n/2-1]);
		sc.close();
	}

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

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

} public class Main {

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

} 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[] a = new int[(int) n];
		for (int i=0; i<n; i++) {
			a[i] = sc.nextInt();
		}
		Arrays.sort(a);
		System.out.println(a[n/2] - a[n/2-1]);
		sc.close();
	}

}