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

public class Main {

    private static final int MOD = 1_000_000_007;

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

        int N = sc.nextInt();

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

        Arrays.sort(d);

        int center = N / 2;

        System.out.println(d[center] - d[center - 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