import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
 


public class Main {
	static int a1[]= {0,-1,0,1};
	static int b1[]= {-1,0,1,0};
	private static Scanner sc = new Scanner(System.in);
	//result = Math.pow(num1, num3)
	//StringBuffer str = new StringBuffer(hoge1);
	//String hoge2 = str.reverse().toString();
	//map.containsKey(A)

	//Map<String, Integer> map = new HashMap<String, Integer>(n);
	/*for ( キーのデータ型 key : マップの名前.keySet() ) {
		データのデータ型 data = マップの名前.get( key );
		
		// keyやdataを使った処理;
	}*/
	//int i = Integer.parseInt(s);
	//Queue<String> qq=new ArrayDeque<>(); //add,poll,peek
	//Deque<String> qq=new ArrayDeque<>();//push,pop,peek
	//ArrayList<String> cc = new ArrayList<>(n);
	//Collections.sort(list);
	//Array.sort(list);
	//Arrays.asList(c).contains("a")
	//list.set(1,"walk");
	public static void main(String[] args) {
		int N=sc.nextInt();
		ArrayList<Integer> cc=new ArrayList<>(N);
		for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		}
		Collections.sort(cc);
		p(cc.get(N/2)-cc.get(N/2-1));
		
	}
	static void p(String ans) {System.out.println(ans);};
	static void p(int ans) {System.out.println(ans);};
	static void p() {System.out.println();};
	static void p(long ans) {System.out.println(ans);};
	static void p(double ans) {System.out.println(ans);};
}
	 import java.util.ArrayList; ArrayList java.util import java.util.Collections; Collections java.util import java.util.Scanner; Scanner java.util public class Main {
	static int a1[]= {0,-1,0,1};
	static int b1[]= {-1,0,1,0};
	private static Scanner sc = new Scanner(System.in);
	//result = Math.pow(num1, num3)
	//StringBuffer str = new StringBuffer(hoge1);
	//String hoge2 = str.reverse().toString();
	//map.containsKey(A)

	//Map<String, Integer> map = new HashMap<String, Integer>(n);
	/*for ( キーのデータ型 key : マップの名前.keySet() ) {
		データのデータ型 data = マップの名前.get( key );
		
		// keyやdataを使った処理;
	}*/
	//int i = Integer.parseInt(s);
	//Queue<String> qq=new ArrayDeque<>(); //add,poll,peek
	//Deque<String> qq=new ArrayDeque<>();//push,pop,peek
	//ArrayList<String> cc = new ArrayList<>(n);
	//Collections.sort(list);
	//Array.sort(list);
	//Arrays.asList(c).contains("a")
	//list.set(1,"walk");
	public static void main(String[] args) {
		int N=sc.nextInt();
		ArrayList<Integer> cc=new ArrayList<>(N);
		for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		}
		Collections.sort(cc);
		p(cc.get(N/2)-cc.get(N/2-1));
		
	}
	static void p(String ans) {System.out.println(ans);};
	static void p(int ans) {System.out.println(ans);};
	static void p() {System.out.println();};
	static void p(long ans) {System.out.println(ans);};
	static void p(double ans) {System.out.println(ans);};
} Main static int a1[]= {0,-1,0,1}; a1 {0,-1,0,1} 0 -1 1 0 1 static int b1[]= {-1,0,1,0}; b1 {-1,0,1,0} -1 1 0 1 0 private static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) //Map<String, Integer> map = new HashMap<String, Integer>(n);
	/*for ( キーのデータ型 key : マップの名前.keySet() ) {
		データのデータ型 data = マップの名前.get( key );
		
		// keyやdataを使った処理;
	}*/
	//int i = Integer.parseInt(s);
	//Queue<String> qq=new ArrayDeque<>(); //add,poll,peek
	//Deque<String> qq=new ArrayDeque<>();//push,pop,peek
	//ArrayList<String> cc = new ArrayList<>(n);
	//Collections.sort(list);
	//Array.sort(list);
	//Arrays.asList(c).contains("a")
	//list.set(1,"walk");
	public static void main(String[] args) {
		int N=sc.nextInt();
		ArrayList<Integer> cc=new ArrayList<>(N);
		for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		}
		Collections.sort(cc);
		p(cc.get(N/2)-cc.get(N/2-1));
		
	} main {
		int N=sc.nextInt();
		ArrayList<Integer> cc=new ArrayList<>(N);
		for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		}
		Collections.sort(cc);
		p(cc.get(N/2)-cc.get(N/2-1));
		
	} int N=sc.nextInt(); N sc.nextInt() sc.nextInt sc ArrayList<Integer> cc=new ArrayList<>(N); cc new ArrayList<>(N) for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		} int i=0; int i=0; i 0 i<N i N i++ i++ i {
			cc.add(sc.nextInt());
		} {
			cc.add(sc.nextInt());
		} cc.add(sc.nextInt()) cc.add cc sc.nextInt() sc.nextInt sc Collections.sort(cc) Collections.sort Collections cc p(cc.get(N/2)-cc.get(N/2-1)) p cc.get(N/2)-cc.get(N/2-1) cc.get(N/2) cc.get cc N/2 N 2 cc.get(N/2-1) cc.get cc N/2-1 N/2 N 2 1 String[] args args static void p(String ans) {System.out.println(ans);} p {System.out.println(ans);} System.out.println(ans) System.out.println System.out System System.out ans String ans ans static void p(int ans) {System.out.println(ans);} p {System.out.println(ans);} System.out.println(ans) System.out.println System.out System System.out ans int ans ans static void p() {System.out.println();} p {System.out.println();} System.out.println() System.out.println System.out System System.out static void p(long ans) {System.out.println(ans);} p {System.out.println(ans);} System.out.println(ans) System.out.println System.out System System.out ans long ans ans static void p(double ans) {System.out.println(ans);} p {System.out.println(ans);} System.out.println(ans) System.out.println System.out System System.out ans double ans ans public class Main {
	static int a1[]= {0,-1,0,1};
	static int b1[]= {-1,0,1,0};
	private static Scanner sc = new Scanner(System.in);
	//result = Math.pow(num1, num3)
	//StringBuffer str = new StringBuffer(hoge1);
	//String hoge2 = str.reverse().toString();
	//map.containsKey(A)

	//Map<String, Integer> map = new HashMap<String, Integer>(n);
	/*for ( キーのデータ型 key : マップの名前.keySet() ) {
		データのデータ型 data = マップの名前.get( key );
		
		// keyやdataを使った処理;
	}*/
	//int i = Integer.parseInt(s);
	//Queue<String> qq=new ArrayDeque<>(); //add,poll,peek
	//Deque<String> qq=new ArrayDeque<>();//push,pop,peek
	//ArrayList<String> cc = new ArrayList<>(n);
	//Collections.sort(list);
	//Array.sort(list);
	//Arrays.asList(c).contains("a")
	//list.set(1,"walk");
	public static void main(String[] args) {
		int N=sc.nextInt();
		ArrayList<Integer> cc=new ArrayList<>(N);
		for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		}
		Collections.sort(cc);
		p(cc.get(N/2)-cc.get(N/2-1));
		
	}
	static void p(String ans) {System.out.println(ans);};
	static void p(int ans) {System.out.println(ans);};
	static void p() {System.out.println();};
	static void p(long ans) {System.out.println(ans);};
	static void p(double ans) {System.out.println(ans);};
} public class Main {
	static int a1[]= {0,-1,0,1};
	static int b1[]= {-1,0,1,0};
	private static Scanner sc = new Scanner(System.in);
	//result = Math.pow(num1, num3)
	//StringBuffer str = new StringBuffer(hoge1);
	//String hoge2 = str.reverse().toString();
	//map.containsKey(A)

	//Map<String, Integer> map = new HashMap<String, Integer>(n);
	/*for ( キーのデータ型 key : マップの名前.keySet() ) {
		データのデータ型 data = マップの名前.get( key );
		
		// keyやdataを使った処理;
	}*/
	//int i = Integer.parseInt(s);
	//Queue<String> qq=new ArrayDeque<>(); //add,poll,peek
	//Deque<String> qq=new ArrayDeque<>();//push,pop,peek
	//ArrayList<String> cc = new ArrayList<>(n);
	//Collections.sort(list);
	//Array.sort(list);
	//Arrays.asList(c).contains("a")
	//list.set(1,"walk");
	public static void main(String[] args) {
		int N=sc.nextInt();
		ArrayList<Integer> cc=new ArrayList<>(N);
		for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		}
		Collections.sort(cc);
		p(cc.get(N/2)-cc.get(N/2-1));
		
	}
	static void p(String ans) {System.out.println(ans);};
	static void p(int ans) {System.out.println(ans);};
	static void p() {System.out.println();};
	static void p(long ans) {System.out.println(ans);};
	static void p(double ans) {System.out.println(ans);};
} Main
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
 


public class Main {
	static int a1[]= {0,-1,0,1};
	static int b1[]= {-1,0,1,0};
	private static Scanner sc = new Scanner(System.in);
	//result = Math.pow(num1, num3)
	//StringBuffer str = new StringBuffer(hoge1);
	//String hoge2 = str.reverse().toString();
	//map.containsKey(A)

	//Map<String, Integer> map = new HashMap<String, Integer>(n);
	/*for ( キーのデータ型 key : マップの名前.keySet() ) {
		データのデータ型 data = マップの名前.get( key );
		
		// keyやdataを使った処理;
	}*/
	//int i = Integer.parseInt(s);
	//Queue<String> qq=new ArrayDeque<>(); //add,poll,peek
	//Deque<String> qq=new ArrayDeque<>();//push,pop,peek
	//ArrayList<String> cc = new ArrayList<>(n);
	//Collections.sort(list);
	//Array.sort(list);
	//Arrays.asList(c).contains("a")
	//list.set(1,"walk");
	public static void main(String[] args) {
		int N=sc.nextInt();
		ArrayList<Integer> cc=new ArrayList<>(N);
		for(int i=0;i<N;i++) {
			cc.add(sc.nextInt());
		}
		Collections.sort(cc);
		p(cc.get(N/2)-cc.get(N/2-1));
		
	}
	static void p(String ans) {System.out.println(ans);};
	static void p(int ans) {System.out.println(ans);};
	static void p() {System.out.println();};
	static void p(long ans) {System.out.println(ans);};
	static void p(double ans) {System.out.println(ans);};
}
	