import java.util.*;

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

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] X = new int[N];
		for(int i = 0; i < N; i++) {
			X[i] = sc.nextInt();
		}
		Arrays.sort(X);
		int min = X[N / 2 - 1];
		int max = X[N / 2];
		
		System.out.println(max-min);
	}
}
/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