import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int n_half = n/2;

    int[] d = new int[n];

    for(int i=0; i<n; i++){
      d[i] = sc.nextInt();
    }
    //配列のソート
    Arrays.sort(d);


    int small_diff = d[n_half-1];
    int big_diff = d[n_half];
    int ans = d[n_half]-d[n_half-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 n_half = n/2;

    int[] d = new int[n];

    for(int i=0; i<n; i++){
      d[i] = sc.nextInt();
    }
    //配列のソート
    Arrays.sort(d);


    int small_diff = d[n_half-1];
    int big_diff = d[n_half];
    int ans = d[n_half]-d[n_half-1];

    System.out.println(ans);


  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int n_half = n/2;

    int[] d = new int[n];

    for(int i=0; i<n; i++){
      d[i] = sc.nextInt();
    }
    //配列のソート
    Arrays.sort(d);


    int small_diff = d[n_half-1];
    int big_diff = d[n_half];
    int ans = d[n_half]-d[n_half-1];

    System.out.println(ans);


  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int n_half = n/2;

    int[] d = new int[n];

    for(int i=0; i<n; i++){
      d[i] = sc.nextInt();
    }
    //配列のソート
    Arrays.sort(d);


    int small_diff = d[n_half-1];
    int big_diff = d[n_half];
    int ans = d[n_half]-d[n_half-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 n_half = n/2; n_half n/2 n 2 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 small_diff = d[n_half-1]; small_diff d[n_half-1] d n_half-1 n_half 1 int big_diff = d[n_half]; big_diff d[n_half] d n_half int ans = d[n_half]-d[n_half-1]; ans d[n_half]-d[n_half-1] d[n_half] d n_half d[n_half-1] d n_half-1 n_half 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 n_half = n/2;

    int[] d = new int[n];

    for(int i=0; i<n; i++){
      d[i] = sc.nextInt();
    }
    //配列のソート
    Arrays.sort(d);


    int small_diff = d[n_half-1];
    int big_diff = d[n_half];
    int ans = d[n_half]-d[n_half-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 n_half = n/2;

    int[] d = new int[n];

    for(int i=0; i<n; i++){
      d[i] = sc.nextInt();
    }
    //配列のソート
    Arrays.sort(d);


    int small_diff = d[n_half-1];
    int big_diff = d[n_half];
    int ans = d[n_half]-d[n_half-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 n_half = n/2;

    int[] d = new int[n];

    for(int i=0; i<n; i++){
      d[i] = sc.nextInt();
    }
    //配列のソート
    Arrays.sort(d);


    int small_diff = d[n_half-1];
    int big_diff = d[n_half];
    int ans = d[n_half]-d[n_half-1];

    System.out.println(ans);


  }
}