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 sum =0;
		sum = a[a.length/2]-a[a.length/2-1];
		System.out.print(sum);
	}
} 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 sum =0;
		sum = a[a.length/2]-a[a.length/2-1];
		System.out.print(sum);
	}
} 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 sum =0;
		sum = a[a.length/2]-a[a.length/2-1];
		System.out.print(sum);
	} 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 sum =0;
		sum = a[a.length/2]-a[a.length/2-1];
		System.out.print(sum);
	} 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 sum =0; sum 0 sum = a[a.length/2]-a[a.length/2-1] sum a[a.length/2]-a[a.length/2-1] a[a.length/2] a a.length/2 a.length a a.length 2 a[a.length/2-1] a a.length/2-1 a.length/2 a.length a a.length 2 1 System.out.print(sum) System.out.print System.out System System.out sum 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 sum =0;
		sum = a[a.length/2]-a[a.length/2-1];
		System.out.print(sum);
	}
} 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 sum =0;
		sum = a[a.length/2]-a[a.length/2-1];
		System.out.print(sum);
	}
} 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 sum =0;
		sum = a[a.length/2]-a[a.length/2-1];
		System.out.print(sum);
	}
}
