import 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);
    System.out.println(d[N/2-1] == d[N/2] ? 0 : d[N/2]-d[N/2-1]);
  }
} import java.util.*; util.* java 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/2-1] == d[N/2] ? 0 : 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/2-1] == d[N/2] ? 0 : 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/2-1] == d[N/2] ? 0 : 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 System.out.println(d[N/2-1] == d[N/2] ? 0 : d[N/2]-d[N/2-1]) System.out.println System.out System System.out d[N/2-1] == d[N/2] ? 0 : 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 0 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.*;

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/2-1] == d[N/2] ? 0 : d[N/2]-d[N/2-1]);
  }
}