import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

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

}
/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