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[] d = new int[n];
        for (int i = 0; i < n; i++) {
            d[i] = sc.nextInt();
        }

        int ans = solve(n, d);
        System.out.println(ans);
    }

    static int solve(int n, int[] d) {
        Arrays.sort(d);

        int arc = d[n / 2];
        int abc = d[n / 2 - 1];
        return arc - abc;
    }
} 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[] d = new int[n];
        for (int i = 0; i < n; i++) {
            d[i] = sc.nextInt();
        }

        int ans = solve(n, d);
        System.out.println(ans);
    }

    static int solve(int n, int[] d) {
        Arrays.sort(d);

        int arc = d[n / 2];
        int abc = d[n / 2 - 1];
        return arc - abc;
    }
} Main public static void main(String[] args) {

        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();
        }

        int ans = solve(n, d);
        System.out.println(ans);
    } 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();
        }

        int ans = solve(n, d);
        System.out.println(ans);
    } 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 int ans = solve(n, d); ans solve(n, d) solve n d System.out.println(ans) System.out.println System.out System System.out ans String[] args args static int solve(int n, int[] d) {
        Arrays.sort(d);

        int arc = d[n / 2];
        int abc = d[n / 2 - 1];
        return arc - abc;
    } solve {
        Arrays.sort(d);

        int arc = d[n / 2];
        int abc = d[n / 2 - 1];
        return arc - abc;
    } Arrays.sort(d) Arrays.sort Arrays d int arc = d[n / 2]; arc d[n / 2] d n / 2 n 2 int abc = d[n / 2 - 1]; abc d[n / 2 - 1] d n / 2 - 1 n / 2 n 2 1 return arc - abc; arc - abc arc abc int n n int[] d d public class Main {

    public static void main(String[] args) {

        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();
        }

        int ans = solve(n, d);
        System.out.println(ans);
    }

    static int solve(int n, int[] d) {
        Arrays.sort(d);

        int arc = d[n / 2];
        int abc = d[n / 2 - 1];
        return arc - abc;
    }
} public class Main {

    public static void main(String[] args) {

        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();
        }

        int ans = solve(n, d);
        System.out.println(ans);
    }

    static int solve(int n, int[] d) {
        Arrays.sort(d);

        int arc = d[n / 2];
        int abc = d[n / 2 - 1];
        return arc - abc;
    }
} 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[] d = new int[n];
        for (int i = 0; i < n; i++) {
            d[i] = sc.nextInt();
        }

        int ans = solve(n, d);
        System.out.println(ans);
    }

    static int solve(int n, int[] d) {
        Arrays.sort(d);

        int arc = d[n / 2];
        int abc = d[n / 2 - 1];
        return arc - abc;
    }
}
