import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int N = sc.nextInt();
		int[] d = new int[N];
		for(int i=0; i<N; i++)d[i] = sc.nextInt();
		Arrays.sort(d);
		out.println(d[N/2] - d[N/2-1]);

		out.flush();
	}
} import java.io.PrintWriter; PrintWriter java.io import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int N = sc.nextInt();
		int[] d = new int[N];
		for(int i=0; i<N; i++)d[i] = sc.nextInt();
		Arrays.sort(d);
		out.println(d[N/2] - d[N/2-1]);

		out.flush();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int N = sc.nextInt();
		int[] d = new int[N];
		for(int i=0; i<N; i++)d[i] = sc.nextInt();
		Arrays.sort(d);
		out.println(d[N/2] - d[N/2-1]);

		out.flush();
	} main {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int N = sc.nextInt();
		int[] d = new int[N];
		for(int i=0; i<N; i++)d[i] = sc.nextInt();
		Arrays.sort(d);
		out.println(d[N/2] - d[N/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) 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] d i sc.nextInt() sc.nextInt sc Arrays.sort(d) Arrays.sort Arrays d out.println(d[N/2] - d[N/2-1]) out.println 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 out.flush() out.flush out String[] args args
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		int N = sc.nextInt();
		int[] d = new int[N];
		for(int i=0; i<N; i++)d[i] = sc.nextInt();
		Arrays.sort(d);
		out.println(d[N/2] - d[N/2-1]);

		out.flush();
	}
}
