import java.util.*;
import static java.lang.Math.*;
import java.math.BigInteger;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0; i < n; i++){
		    d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		
		// 計算
		int result = d[n/2] - d[n/2 - 1];
		
		// 出力
		System.out.println(result);
		
	}
} import java.util.*; util.* java import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.Math.*; import java.math.BigInteger; BigInteger java.math public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0; i < n; i++){
		    d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		
		// 計算
		int result = d[n/2] - d[n/2 - 1];
		
		// 出力
		System.out.println(result);
		
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0; i < n; i++){
		    d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		
		// 計算
		int result = d[n/2] - d[n/2 - 1];
		
		// 出力
		System.out.println(result);
		
	} main {
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0; i < n; i++){
		    d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		
		// 計算
		int result = d[n/2] - d[n/2 - 1];
		
		// 出力
		System.out.println(result);
		
	} 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 result = d[n/2] - d[n/2 - 1]; result d[n/2] - d[n/2 - 1] d[n/2] d n/2 n 2 d[n/2 - 1] d n/2 - 1 n/2 n 2 1 System.out.println(result) System.out.println System.out System System.out result String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0; i < n; i++){
		    d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		
		// 計算
		int result = d[n/2] - d[n/2 - 1];
		
		// 出力
		System.out.println(result);
		
	}
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0; i < n; i++){
		    d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		
		// 計算
		int result = d[n/2] - d[n/2 - 1];
		
		// 出力
		System.out.println(result);
		
	}
} Main
import java.util.*;
import static java.lang.Math.*;
import java.math.BigInteger;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int[] d = new int[n];
		for(int i = 0; i < n; i++){
		    d[i] = sc.nextInt();
		}
		Arrays.sort(d);
		
		// 計算
		int result = d[n/2] - d[n/2 - 1];
		
		// 出力
		System.out.println(result);
		
	}
}
