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

// 15
class Main{

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] a = new int[N];
        for(int i = 0; i < N; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        int ans = a[N / 2] - a[N / 2 - 1];

        System.out.println(ans);
    }

} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util class Main{

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] a = new int[N];
        for(int i = 0; i < N; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        int ans = a[N / 2] - a[N / 2 - 1];

        System.out.println(ans);
    }

} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] a = new int[N];
        for(int i = 0; i < N; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        int ans = a[N / 2] - a[N / 2 - 1];

        System.out.println(ans);
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] a = new int[N];
        for(int i = 0; i < N; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        int ans = a[N / 2] - a[N / 2 - 1];

        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[] a = new int[N]; a new int[N] N for(int i = 0; i < N; i++)
            a[i] = sc.nextInt(); int i = 0; int i = 0; i 0 i < N i N i++ i++ i a[i] = sc.nextInt(); a[i] = sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc Arrays.sort(a) Arrays.sort Arrays a int ans = a[N / 2] - a[N / 2 - 1]; ans 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 System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import java.util.Arrays;
import java.util.Scanner;

// 15
class Main{

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] a = new int[N];
        for(int i = 0; i < N; i++)
            a[i] = sc.nextInt();

        Arrays.sort(a);
        int ans = a[N / 2] - a[N / 2 - 1];

        System.out.println(ans);
    }

}
