import java.util.*;
import static java.lang.System.*;

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 a = d[N/2 - 1];
	  int b = d[N/2];
	  int ans = b-a;
	  
	  out.print(ans);
  	}
  }	  import java.util.*; util.* java import static java.lang.System.*; import static java.lang.System.*; import static java.lang.System.*; 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 a = d[N/2 - 1];
	  int b = d[N/2];
	  int ans = b-a;
	  
	  out.print(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 a = d[N/2 - 1];
	  int b = d[N/2];
	  int ans = b-a;
	  
	  out.print(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 a = d[N/2 - 1];
	  int b = d[N/2];
	  int ans = b-a;
	  
	  out.print(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] d i sc.nextInt() sc.nextInt sc Arrays.sort(d) Arrays.sort Arrays d int a = d[N/2 - 1]; a d[N/2 - 1] d N/2 - 1 N/2 N 2 1 int b = d[N/2]; b d[N/2] d N/2 N 2 int ans = b-a; ans b-a b a out.print(ans) out.print 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 a = d[N/2 - 1];
	  int b = d[N/2];
	  int ans = b-a;
	  
	  out.print(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 a = d[N/2 - 1];
	  int b = d[N/2];
	  int ans = b-a;
	  
	  out.print(ans);
  	}
  } Main
import java.util.*;
import static java.lang.System.*;

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 a = d[N/2 - 1];
	  int b = d[N/2];
	  int ans = b-a;
	  
	  out.print(ans);
  	}
  }	 