import java.util.*;

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

        System.out.println(b-a);
        sc.close();
    }
}
/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