import java.util.Arrays;
import java.util.Scanner;

public class Main {

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

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

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

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];
		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		if (A[N/2-1]==A[N/2]) {
			System.out.println(0);
			return;
		}
		System.out.println(A[N/2]-A[N/2-1]);
	}
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];
		for (int i = 0; i < N; i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		if (A[N/2-1]==A[N/2]) {
			System.out.println(0);
			return;
		}
		System.out.println(A[N/2]-A[N/2-1]);
	}
}