import java.util.*;

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

        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        }
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        }
    }
} Main public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        }
    } main {

        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        }
    } 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[] ary = new int[n]; ary new int[n] n for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            ary[i] = Integer.parseInt(sc.next());
        } {
            ary[i] = Integer.parseInt(sc.next());
        } ary[i] = Integer.parseInt(sc.next()) ary[i] ary i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc Arrays.sort(ary) Arrays.sort Arrays ary if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        } ary[ary.length/2] == ary[ary.length/2 -1] ary[ary.length/2] ary ary.length/2 ary.length ary ary.length 2 ary[ary.length/2 -1] ary ary.length/2 -1 ary.length/2 ary.length ary ary.length 2 1 {
            System.out.print("0");
        } System.out.print("0") System.out.print System.out System System.out "0" {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        } System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]) System.out.print System.out System System.out ary[ary.length/2] - ary[ary.length/2 - 1] ary[ary.length/2] ary ary.length/2 ary.length ary ary.length 2 ary[ary.length/2 - 1] ary ary.length/2 - 1 ary.length/2 ary.length ary ary.length 2 1 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[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        }
    }
} public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        }
    }
} Main
import java.util.*;

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

        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/2 - 1]);
        }
    }
}
