import java.util.*;
class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int[] d=new int[n];
		for(int i=0;i<n;i++){
			d[i]=sc.nextInt();
		}
		Arrays.sort(d);
		int p=n/2;
		int q=n/2-1;
		if(d[p]==d[q]){
			System.out.println(0);
		}else{
			System.out.println(d[p]-d[q]);
		}
	}
} import java.util.*; util.* java class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int[] d=new int[n];
		for(int i=0;i<n;i++){
			d[i]=sc.nextInt();
		}
		Arrays.sort(d);
		int p=n/2;
		int q=n/2-1;
		if(d[p]==d[q]){
			System.out.println(0);
		}else{
			System.out.println(d[p]-d[q]);
		}
	}
} Main public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int[] d=new int[n];
		for(int i=0;i<n;i++){
			d[i]=sc.nextInt();
		}
		Arrays.sort(d);
		int p=n/2;
		int q=n/2-1;
		if(d[p]==d[q]){
			System.out.println(0);
		}else{
			System.out.println(d[p]-d[q]);
		}
	} main {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int[] d=new int[n];
		for(int i=0;i<n;i++){
			d[i]=sc.nextInt();
		}
		Arrays.sort(d);
		int p=n/2;
		int q=n/2-1;
		if(d[p]==d[q]){
			System.out.println(0);
		}else{
			System.out.println(d[p]-d[q]);
		}
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] d=new int[n]; d new int[n] n for(int i=0;i<n;i++){
			d[i]=sc.nextInt();
		} int i=0; int i=0; i 0 i<n i n i++ i++ i {
			d[i]=sc.nextInt();
		} {
			d[i]=sc.nextInt();
		} d[i]=sc.nextInt() d[i] d i sc.nextInt() sc.nextInt sc Arrays.sort(d) Arrays.sort Arrays d int p=n/2; p n/2 n 2 int q=n/2-1; q n/2-1 n/2 n 2 1 if(d[p]==d[q]){
			System.out.println(0);
		}else{
			System.out.println(d[p]-d[q]);
		} d[p]==d[q] d[p] d p d[q] d q {
			System.out.println(0);
		} System.out.println(0) System.out.println System.out System System.out 0 {
			System.out.println(d[p]-d[q]);
		} System.out.println(d[p]-d[q]) System.out.println System.out System System.out d[p]-d[q] d[p] d p d[q] d q String[] args args
import java.util.*;
class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int[] d=new int[n];
		for(int i=0;i<n;i++){
			d[i]=sc.nextInt();
		}
		Arrays.sort(d);
		int p=n/2;
		int q=n/2-1;
		if(d[p]==d[q]){
			System.out.println(0);
		}else{
			System.out.println(d[p]-d[q]);
		}
	}
}