
import java.util.Arrays;
import java.util.Scanner;

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

        int N = sc.nextInt();
        if (N % 2 == 1) {
            System.out.println(0);
            return;
        }
        int[] d = new int[N];

        for (int i = 0; i < N; i++) d[i] = sc.nextInt();

        Arrays.sort(d);

        System.out.println(d[N / 2] - d[N / 2 - 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