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();
    }

    Arrays.sort(d);

    System.out.println(d[n / 2] - d[(n / 2) - 1]);

  }
} 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();
    }

    Arrays.sort(d);

    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);

    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);

    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] = sc.nextInt() d[i] d i sc.nextInt() sc.nextInt sc Arrays.sort(d) Arrays.sort Arrays d 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 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();
    }

    Arrays.sort(d);

    System.out.println(d[n / 2] - d[(n / 2) - 1]);

  }
} 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();
    }

    Arrays.sort(d);

    System.out.println(d[n / 2] - d[(n / 2) - 1]);

  }
} 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();
    }

    Arrays.sort(d);

    System.out.println(d[n / 2] - d[(n / 2) - 1]);

  }
}