import 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 ans = 0;
    int mid = N/2;
    if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-1];
    }
    System.out.println(ans);
  }
} import java.util.*; util.* java 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 ans = 0;
    int mid = N/2;
    if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-1];
    }
    System.out.println(ans);
  }
} 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 ans = 0;
    int mid = N/2;
    if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-1];
    }
    System.out.println(ans);
  } 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 ans = 0;
    int mid = N/2;
    if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-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[] 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 ans = 0; ans 0 int mid = N/2; mid N/2 N 2 if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-1];
    } d[mid] != d[mid-1] d[mid] d mid d[mid-1] d mid-1 mid 1 {
      ans = d[mid] - d[mid-1];
    } ans = d[mid] - d[mid-1] ans d[mid] - d[mid-1] d[mid] d mid d[mid-1] d mid-1 mid 1 System.out.println(ans) System.out.println System.out System System.out ans 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 ans = 0;
    int mid = N/2;
    if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-1];
    }
    System.out.println(ans);
  }
} 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 ans = 0;
    int mid = N/2;
    if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-1];
    }
    System.out.println(ans);
  }
} Main
import 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 ans = 0;
    int mid = N/2;
    if (d[mid] != d[mid-1]) {
      ans = d[mid] - d[mid-1];
    }
    System.out.println(ans);
  }
}