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);

        if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-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 d[] = new int[n];

        for (int i=0; i<n; i++){
            d[i] = sc.nextInt();
        }


        Arrays.sort(d);

        if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-1]);
        }


        }
    } 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);

        if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-1]);
        }


        } 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);

        if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-1]);
        }


        } 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 if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-1]);
        } n%2!=0 n%2 n 2 0 {
            System.out.println(0);
        } System.out.println(0) System.out.println System.out System System.out 0 if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-1]);
        } d[(n/2)-1]==d[n/2] d[(n/2)-1] d (n/2)-1 (n/2) n 2 1 d[n/2] d n/2 n 2 {
            System.out.println(0);
        } System.out.println(0) System.out.println System.out System System.out 0 {
            System.out.println(d[n/2]-d[(n/2)-1]);
        } System.out.println(d[n/2]-d[(n/2)-1]) System.out.println System.out System System.out d[n/2]-d[(n/2)-1] d[n/2] d n/2 n 2 d[(n/2)-1] d (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 d[] = new int[n];

        for (int i=0; i<n; i++){
            d[i] = sc.nextInt();
        }


        Arrays.sort(d);

        if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-1]);
        }


        }
    } 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);

        if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-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 d[] = new int[n];

        for (int i=0; i<n; i++){
            d[i] = sc.nextInt();
        }


        Arrays.sort(d);

        if (n%2!=0){
            System.out.println(0);
        }else if(d[(n/2)-1]==d[n/2]){
            System.out.println(0);
        }else{
            System.out.println(d[n/2]-d[(n/2)-1]);
        }


        }
    }
