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 = sc.nextInt();
		int[] d = new int[n];
		for(int i=0;i<n;i++) {
			d[i]=sc.nextInt();
		}
		Arrays.parallelSort(d);
		int abc=d[n/2-1];
		int agc=d[n/2];
		int count=0;
		for(int i=abc+1;i<=agc;i++) {
			count++;
		}
		System.out.println(count);
	}
}

/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