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

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		final int n = sc.nextInt();
		final int nHalf = n / 2;

		List<Integer> list = new ArrayList<Integer>();
		for (int i = 0; i < n; i++) {
			list.add(sc.nextInt());
		}

		Collections.sort(list);

		final int numHalf = list.get(nHalf - 1);
		final int numHalfNext = list.get(nHalf);

		if (numHalf == numHalfNext) {
			System.out.print(0);
			return;
		}

		System.out.print(numHalfNext - numHalf);

	}

}
/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