import java.util.*;
import java.io.*;



public class Main{
    static int INFTY=Integer.MAX_VALUE;
    public static void main (String args[]){
        //初期処理
        Scanner sc=new Scanner(System.in);
        // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        // try{
            // int n = Integer.parseInt(br.readLine());
            
        int n=sc.nextInt();
        int[] arr = new int[n];
        int ans =0;

        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        }
        
        Arrays.sort(arr);
        if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        }
        System.out.println(ans);
    }
} import java.util.*; util.* java import java.io.*; io.* java public class Main{
    static int INFTY=Integer.MAX_VALUE;
    public static void main (String args[]){
        //初期処理
        Scanner sc=new Scanner(System.in);
        // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        // try{
            // int n = Integer.parseInt(br.readLine());
            
        int n=sc.nextInt();
        int[] arr = new int[n];
        int ans =0;

        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        }
        
        Arrays.sort(arr);
        if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        }
        System.out.println(ans);
    }
} Main static int INFTY=Integer.MAX_VALUE; INFTY Integer.MAX_VALUE Integer Integer.MAX_VALUE public static void main (String args[]){
        //初期処理
        Scanner sc=new Scanner(System.in);
        // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        // try{
            // int n = Integer.parseInt(br.readLine());
            
        int n=sc.nextInt();
        int[] arr = new int[n];
        int ans =0;

        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        }
        
        Arrays.sort(arr);
        if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        }
        System.out.println(ans);
    } main {
        //初期処理
        Scanner sc=new Scanner(System.in);
        // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        // try{
            // int n = Integer.parseInt(br.readLine());
            
        int n=sc.nextInt();
        int[] arr = new int[n];
        int ans =0;

        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        }
        
        Arrays.sort(arr);
        if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        }
        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[] arr = new int[n]; arr new int[n] n int ans =0; ans 0 for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        } int i=0; int i=0; i 0 i<n i n i++ i++ i {
            arr[i]=sc.nextInt();
        } {
            arr[i]=sc.nextInt();
        } arr[i]=sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc Arrays.sort(arr) Arrays.sort Arrays arr if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        } arr[n/2-1]==arr[n/2] arr[n/2-1] arr n/2-1 n/2 n 2 1 arr[n/2] arr n/2 n 2 {
            ans=0;
        } ans=0 ans 0 {
            ans=arr[n/2]-arr[n/2-1];
        } ans=arr[n/2]-arr[n/2-1] ans arr[n/2]-arr[n/2-1] arr[n/2] arr n/2 n 2 arr[n/2-1] arr n/2-1 n/2 n 2 1 System.out.println(ans) System.out.println System.out System System.out ans String args[] args public class Main{
    static int INFTY=Integer.MAX_VALUE;
    public static void main (String args[]){
        //初期処理
        Scanner sc=new Scanner(System.in);
        // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        // try{
            // int n = Integer.parseInt(br.readLine());
            
        int n=sc.nextInt();
        int[] arr = new int[n];
        int ans =0;

        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        }
        
        Arrays.sort(arr);
        if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        }
        System.out.println(ans);
    }
} public class Main{
    static int INFTY=Integer.MAX_VALUE;
    public static void main (String args[]){
        //初期処理
        Scanner sc=new Scanner(System.in);
        // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        // try{
            // int n = Integer.parseInt(br.readLine());
            
        int n=sc.nextInt();
        int[] arr = new int[n];
        int ans =0;

        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        }
        
        Arrays.sort(arr);
        if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        }
        System.out.println(ans);
    }
} Main
import java.util.*;
import java.io.*;



public class Main{
    static int INFTY=Integer.MAX_VALUE;
    public static void main (String args[]){
        //初期処理
        Scanner sc=new Scanner(System.in);
        // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        // try{
            // int n = Integer.parseInt(br.readLine());
            
        int n=sc.nextInt();
        int[] arr = new int[n];
        int ans =0;

        for(int i=0;i<n;i++){
            arr[i]=sc.nextInt();
        }
        
        Arrays.sort(arr);
        if(arr[n/2-1]==arr[n/2]){
            ans=0;
        }else{
            ans=arr[n/2]-arr[n/2-1];
        }
        System.out.println(ans);
    }
}