import java.util.*;
import java.math.*;
import java.lang.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	}

} import java.util.*; util.* java import java.math.*; math.* java import java.lang.*; lang.* java public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	} main {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc List<Integer> list = new ArrayList<>(); list new ArrayList<>() for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			list.add(sc.nextInt());
		} {
			list.add(sc.nextInt());
		} list.add(sc.nextInt()) list.add list sc.nextInt() sc.nextInt sc Collections.sort(list) Collections.sort Collections list int halfN = n/2; halfN n/2 n 2 int lessD = list.get(halfN-1); lessD list.get(halfN-1) list.get list halfN-1 halfN 1 int greatD = list.get(halfN); greatD list.get(halfN) list.get list halfN System.out.println(greatD-lessD) System.out.println System.out System System.out greatD-lessD greatD lessD String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	}

} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	}

} Main
import java.util.*;
import java.math.*;
import java.lang.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	}

}
