import java.util.*;
import java.io.*;
import java.awt.*;
import java.awt.geom.*;
import static java.lang.System.*;
import static java.lang.Math.*;
public class Main {
    static Scanner sc=new Scanner(in);
    public static void main(String[] args) {
        int n=sc.nextInt();
        int[] d=new int[n];
        int ans=0;
        for (int i = 0; i < n; i++) {
            d[i]=sc.nextInt();
        }
        Arrays.sort(d);
        ans=max(0,d[n/2]-d[n/2-1]);
        out.println(ans);
    }
}
/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