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