import java.util.*;
import java.math.*;
import java.lang.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 整数の入力
		int n = sc.nextInt();
		List<Integer> list = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		int halfN = n/2;
		int lessD = list.get(halfN-1);
		int greatD = list.get(halfN);




		System.out.println(greatD-lessD);

	}

}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz