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

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();

	Arrays.sort(d);
	if (d[(N / 2) - 1] == d[N / 2])
	    System.out.println(0);
	else
	    System.out.println(d[N / 2] - d[(N / 2) - 1]);
    }
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays java.util 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();

	Arrays.sort(d);
	if (d[(N / 2) - 1] == d[N / 2])
	    System.out.println(0);
	else
	    System.out.println(d[N / 2] - d[(N / 2) - 1]);
    }
} 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();

	Arrays.sort(d);
	if (d[(N / 2) - 1] == d[N / 2])
	    System.out.println(0);
	else
	    System.out.println(d[N / 2] - d[(N / 2) - 1]);
    } 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();

	Arrays.sort(d);
	if (d[(N / 2) - 1] == d[N / 2])
	    System.out.println(0);
	else
	    System.out.println(d[N / 2] - d[(N / 2) - 1]);
    } 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] d i sc.nextInt() sc.nextInt sc Arrays.sort(d) Arrays.sort Arrays d if (d[(N / 2) - 1] == d[N / 2])
	    System.out.println(0);
	else
	    System.out.println(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 System.out.println(0) System.out.println System.out System System.out 0 System.out.println(d[N / 2] - d[(N / 2) - 1]) System.out.println System.out System System.out 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 String[] args args
import java.util.Scanner;
import java.util.Arrays;

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();

	Arrays.sort(d);
	if (d[(N / 2) - 1] == d[N / 2])
	    System.out.println(0);
	else
	    System.out.println(d[N / 2] - d[(N / 2) - 1]);
    }
}