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 = Integer.parseInt(sc.next());
		int[] d = new int[N];

		int idx;
		for (idx = 0; idx < N; idx++) {
			d[idx] = Integer.parseInt(sc.next());
		}

		Arrays.sort(d);

		int low = d[N / 2 - 1];
		int high = d[N / 2];

		System.out.println(high - low);

	}

}

/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