import java.util.*;

class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        int[] d = new int[N];
        
        for(int i = 0; i < N; i++) {
            d[i] = Integer.parseInt(sc.next());
        }

        Arrays.sort(d);
        
        int ans = 0;
        if(d[N/2-1] == d[N/2]) {
            System.out.println(ans);
        }else {
            System.out.println(d[N/2] - d[N/2-1]);
        }
    }
} import java.util.*; util.* java class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        int[] d = new int[N];
        
        for(int i = 0; i < N; i++) {
            d[i] = Integer.parseInt(sc.next());
        }

        Arrays.sort(d);
        
        int ans = 0;
        if(d[N/2-1] == d[N/2]) {
            System.out.println(ans);
        }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 = Integer.parseInt(sc.next());
        int[] d = new int[N];
        
        for(int i = 0; i < N; i++) {
            d[i] = Integer.parseInt(sc.next());
        }

        Arrays.sort(d);
        
        int ans = 0;
        if(d[N/2-1] == d[N/2]) {
            System.out.println(ans);
        }else {
            System.out.println(d[N/2] - d[N/2-1]);
        }
    } main {
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        int[] d = new int[N];
        
        for(int i = 0; i < N; i++) {
            d[i] = Integer.parseInt(sc.next());
        }

        Arrays.sort(d);
        
        int ans = 0;
        if(d[N/2-1] == d[N/2]) {
            System.out.println(ans);
        }else {
            System.out.println(d[N/2] - d[N/2-1]);
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = Integer.parseInt(sc.next()); N Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int[] d = new int[N]; d new int[N] N for(int i = 0; i < N; i++) {
            d[i] = Integer.parseInt(sc.next());
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            d[i] = Integer.parseInt(sc.next());
        } {
            d[i] = Integer.parseInt(sc.next());
        } d[i] = Integer.parseInt(sc.next()) d[i] d i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc Arrays.sort(d) Arrays.sort Arrays d int ans = 0; ans 0 if(d[N/2-1] == d[N/2]) {
            System.out.println(ans);
        }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(ans);
        } System.out.println(ans) System.out.println System.out System System.out ans {
            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
import java.util.*;

class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        int[] d = new int[N];
        
        for(int i = 0; i < N; i++) {
            d[i] = Integer.parseInt(sc.next());
        }

        Arrays.sort(d);
        
        int ans = 0;
        if(d[N/2-1] == d[N/2]) {
            System.out.println(ans);
        }else {
            System.out.println(d[N/2] - d[N/2-1]);
        }
    }
}