import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int[]a=new int[n];
        for(int i=0;i<n;i++)a[i]=sc.nextInt();
        Arrays.sort(a);
        if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]);
        //else System.out.println((a[n/2]-a[n/2-1]==0)?0:(a[n/2-1]==a[n/2-2])?(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]-1:a[n/2]-a[n/2-1]:(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]:a[n/2]-a[n/2-1]+1);
    }
} 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[]a=new int[n];
        for(int i=0;i<n;i++)a[i]=sc.nextInt();
        Arrays.sort(a);
        if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]);
        //else System.out.println((a[n/2]-a[n/2-1]==0)?0:(a[n/2-1]==a[n/2-2])?(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]-1:a[n/2]-a[n/2-1]:(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]:a[n/2]-a[n/2-1]+1);
    }
} Main public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int[]a=new int[n];
        for(int i=0;i<n;i++)a[i]=sc.nextInt();
        Arrays.sort(a);
        if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]);
        //else System.out.println((a[n/2]-a[n/2-1]==0)?0:(a[n/2-1]==a[n/2-2])?(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]-1:a[n/2]-a[n/2-1]:(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]:a[n/2]-a[n/2-1]+1);
    } main {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int[]a=new int[n];
        for(int i=0;i<n;i++)a[i]=sc.nextInt();
        Arrays.sort(a);
        if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]);
        //else System.out.println((a[n/2]-a[n/2-1]==0)?0:(a[n/2-1]==a[n/2-2])?(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]-1:a[n/2]-a[n/2-1]:(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]:a[n/2]-a[n/2-1]+1);
    } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc int[]a=new int[n]; a new int[n] n for(int i=0;i<n;i++)a[i]=sc.nextInt(); int i=0; int i=0; i 0 i<n i n i++ i++ i a[i]=sc.nextInt(); a[i]=sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc Arrays.sort(a) Arrays.sort Arrays a if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]); n==2 n 2 System.out.println((a[0]==a[1])?0:a[1]-a[0]) System.out.println System.out System System.out (a[0]==a[1])?0:a[1]-a[0] (a[0]==a[1]) a[0] a 0 a[1] a 1 0 a[1]-a[0] a[1] a 1 a[0] a 0 if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]); a[n/2]-a[n/2-1]==0 a[n/2]-a[n/2-1] a[n/2] a n/2 n 2 a[n/2-1] a n/2-1 n/2 n 2 1 0 {
            System.out.println(0);
        } System.out.println(0) System.out.println System.out System System.out 0 System.out.println(a[n/2]-a[n/2-1]) System.out.println System.out System System.out a[n/2]-a[n/2-1] a[n/2] a n/2 n 2 a[n/2-1] a n/2-1 n/2 n 2 1 String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int[]a=new int[n];
        for(int i=0;i<n;i++)a[i]=sc.nextInt();
        Arrays.sort(a);
        if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]);
        //else System.out.println((a[n/2]-a[n/2-1]==0)?0:(a[n/2-1]==a[n/2-2])?(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]-1:a[n/2]-a[n/2-1]:(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]:a[n/2]-a[n/2-1]+1);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int[]a=new int[n];
        for(int i=0;i<n;i++)a[i]=sc.nextInt();
        Arrays.sort(a);
        if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]);
        //else System.out.println((a[n/2]-a[n/2-1]==0)?0:(a[n/2-1]==a[n/2-2])?(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]-1:a[n/2]-a[n/2-1]:(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]:a[n/2]-a[n/2-1]+1);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int[]a=new int[n];
        for(int i=0;i<n;i++)a[i]=sc.nextInt();
        Arrays.sort(a);
        if(n==2)System.out.println((a[0]==a[1])?0:a[1]-a[0]);
        else if(a[n/2]-a[n/2-1]==0){
            System.out.println(0);
        }
        else 
            System.out.println(a[n/2]-a[n/2-1]);
        //else System.out.println((a[n/2]-a[n/2-1]==0)?0:(a[n/2-1]==a[n/2-2])?(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]-1:a[n/2]-a[n/2-1]:(a[n/2]==a[n/2+1])?a[n/2]-a[n/2-1]:a[n/2]-a[n/2-1]+1);
    }
}
