import java.util.*;


class Main{
    public static void main(String argv[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] p = new int[n];
        for(int i=0;i<n;i++){
            p[i]=sc.nextInt();
        }

        Arrays.sort(p);
        int K = p[n/2] - p[n/2-1];
        System.out.println(K);
    }
}
/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