import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");

        final 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);
        out.println(d[d.length/2] - d[(d.length/2)-1]);
        
        out.flush();
    }
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");

        final 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);
        out.println(d[d.length/2] - d[(d.length/2)-1]);
        
        out.flush();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");

        final 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);
        out.println(d[d.length/2] - d[(d.length/2)-1]);
        
        out.flush();
    } main {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");

        final 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);
        out.println(d[d.length/2] - d[(d.length/2)-1]);
        
        out.flush();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) final 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 out.println(d[d.length/2] - d[(d.length/2)-1]) out.println out d[d.length/2] - d[(d.length/2)-1] d[d.length/2] d d.length/2 d.length d d.length 2 d[(d.length/2)-1] d (d.length/2)-1 (d.length/2) d.length d d.length 2 1 out.flush() out.flush out String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");

        final 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);
        out.println(d[d.length/2] - d[(d.length/2)-1]);
        
        out.flush();
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");

        final 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);
        out.println(d[d.length/2] - d[(d.length/2)-1]);
        
        out.flush();
    }
} Main
import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        DecimalFormat df = new DecimalFormat("0.00000000");

        final 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);
        out.println(d[d.length/2] - d[(d.length/2)-1]);
        
        out.flush();
    }
}