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);
        int n = Integer.parseInt(sc.nextLine());
        List<Integer> nums = new ArrayList<>();
        for(int i = 0;i < n;i++) {
            nums.add(sc.nextInt());
        }
        Collections.sort(nums);
        int n1 = nums.get(n / 2 - 1);
        int n2 = nums.get(n / 2);
        System.out.println(n2 - n1);
    }
}
/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