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.sort(A);
		
		int left = N/2;
		
		System.out.println(A[left]-A[left-1]);
		sc.close();

	}

} 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.sort(A);
		
		int left = N/2;
		
		System.out.println(A[left]-A[left-1]);
		sc.close();

	}

} 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.sort(A);
		
		int left = N/2;
		
		System.out.println(A[left]-A[left-1]);
		sc.close();

	} 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.sort(A);
		
		int left = N/2;
		
		System.out.println(A[left]-A[left-1]);
		sc.close();

	} 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.sort(A) Arrays.sort Arrays A int left = N/2; left N/2 N 2 System.out.println(A[left]-A[left-1]) System.out.println System.out System System.out A[left]-A[left-1] A[left] A left A[left-1] A left-1 left 1 sc.close() sc.close sc 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.sort(A);
		
		int left = N/2;
		
		System.out.println(A[left]-A[left-1]);
		sc.close();

	}

} 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.sort(A);
		
		int left = N/2;
		
		System.out.println(A[left]-A[left-1]);
		sc.close();

	}

} 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.sort(A);
		
		int left = N/2;
		
		System.out.println(A[left]-A[left-1]);
		sc.close();

	}

}
