import java.util.*;
import java.util.TreeMap;

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);
    int half = N / 2;
    System.out.println(d[half] - d[half - 1]);
  }
} import java.util.*; util.* java import java.util.TreeMap; TreeMap 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);
    int half = N / 2;
    System.out.println(d[half] - d[half - 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);
    int half = N / 2;
    System.out.println(d[half] - d[half - 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);
    int half = N / 2;
    System.out.println(d[half] - d[half - 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 int half = N / 2; half N / 2 N 2 System.out.println(d[half] - d[half - 1]) System.out.println System.out System System.out d[half] - d[half - 1] d[half] d half d[half - 1] d half - 1 half 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);
    int half = N / 2;
    System.out.println(d[half] - d[half - 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);
    int half = N / 2;
    System.out.println(d[half] - d[half - 1]);
  }
} Main
import java.util.*;
import java.util.TreeMap;

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);
    int half = N / 2;
    System.out.println(d[half] - d[half - 1]);
  }
}
