import java.util.*;

public class Main {

    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int[] array = new int[n];

        for (int i = 0; i < n; i++) {
            array[i] = scan.nextInt();
        }

        Arrays.sort(array);

        int half = array.length / 2;

        if (array[half - 1] == array[half]) {

            System.out.println(0);
            return;
        }

        int ans = 0;
        System.out.println(array[half] - array[half - 1]);

    }
}
/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