import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();

        List<Long> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            long d = sc.nextLong();
            list.add(d);
        }
        Collections.sort(list);

        int index = (list.size() - 1) / 2;
        long min = list.get(index);
        long max = list.get(index + 1);
        System.out.println(max - min);
    }
}
/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