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 = 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);

        int cnt = 0;
        if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = d[n/2] - d[n/2 - 1];
        }

        System.out.println(cnt);
    }
} 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 = 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);

        int cnt = 0;
        if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = d[n/2] - d[n/2 - 1];
        }

        System.out.println(cnt);
    }
} Main public static void main(String[] args) {

        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);

        int cnt = 0;
        if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = d[n/2] - d[n/2 - 1];
        }

        System.out.println(cnt);
    } main {

        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);

        int cnt = 0;
        if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = d[n/2] - d[n/2 - 1];
        }

        System.out.println(cnt);
    } 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 int cnt = 0; cnt 0 if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = 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 {
            cnt = 0;
        } cnt = 0 cnt 0 {
            cnt = d[n/2] - d[n/2 - 1];
        } cnt = d[n/2] - d[n/2 - 1] cnt 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 System.out.println(cnt) System.out.println System.out System System.out cnt String[] args args public class Main {
    public static void main(String[] args) {

        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);

        int cnt = 0;
        if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = d[n/2] - d[n/2 - 1];
        }

        System.out.println(cnt);
    }
} public class Main {
    public static void main(String[] args) {

        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);

        int cnt = 0;
        if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = d[n/2] - d[n/2 - 1];
        }

        System.out.println(cnt);
    }
} 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 = 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);

        int cnt = 0;
        if (d[n/2 - 1] == d[n/2]) {
            cnt = 0;
        } else {
            cnt = d[n/2] - d[n/2 - 1];
        }

        System.out.println(cnt);
    }
}