import java.util.*;

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

    int n = sc.nextInt();
    int halfN = n / 2;

    List<Integer> list = new ArrayList<>();
    for (int i = 0; i < n; i++) {
      list.add(sc.nextInt());
    }

    Collections.sort(list);

    int result = list.get(halfN) - list.get(halfN - 1);

    System.out.println(result);
  }
}

/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