import java.util.*;

class Main {
    public static void main(String[] args) {
        new Solver().run();
    }
}

class Solver {

    public void run() {
        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();
        }
        Arrays.sort(d);


        int pivot = (d.length-1)/2;
        System.out.println(d[pivot + 1] - d[pivot]);

        return;
    }

} import java.util.*; util.* java class Main {
    public static void main(String[] args) {
        new Solver().run();
    }
} Main public static void main(String[] args) {
        new Solver().run();
    } main {
        new Solver().run();
    } new Solver().run() new Solver().run new Solver() String[] args args class Solver {

    public void run() {
        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();
        }
        Arrays.sort(d);


        int pivot = (d.length-1)/2;
        System.out.println(d[pivot + 1] - d[pivot]);

        return;
    }

} Solver public void run() {
        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();
        }
        Arrays.sort(d);


        int pivot = (d.length-1)/2;
        System.out.println(d[pivot + 1] - d[pivot]);

        return;
    } run {
        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();
        }
        Arrays.sort(d);


        int pivot = (d.length-1)/2;
        System.out.println(d[pivot + 1] - d[pivot]);

        return;
    } 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 Arrays.sort(d) Arrays.sort Arrays d int pivot = (d.length-1)/2; pivot (d.length-1)/2 (d.length-1) d.length d d.length 1 2 System.out.println(d[pivot + 1] - d[pivot]) System.out.println System.out System System.out d[pivot + 1] - d[pivot] d[pivot + 1] d pivot + 1 pivot 1 d[pivot] d pivot return;
import java.util.*;

class Main {
    public static void main(String[] args) {
        new Solver().run();
    }
}

class Solver {

    public void run() {
        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();
        }
        Arrays.sort(d);


        int pivot = (d.length-1)/2;
        System.out.println(d[pivot + 1] - d[pivot]);

        return;
    }

}