import java.util.*;

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