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

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

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