import java.util.*;

public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] ary = new int[n];

        for (int i = 0; i < n; i++) {
            ary[i] = Integer.parseInt(sc.next());
        }
        Arrays.sort(ary);

        if (ary[ary.length/2] == ary[ary.length/2 -1]) {
            System.out.print("0");
        } else {
            System.out.print(ary[ary.length/2] - ary[ary.length/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