 import java.util.*; 
 
public class Main{  
  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);
    for(int i=0; i<N; i++){
      System.out.println(d[N/2]-d[N/2-1]);
      break;
    }
  }
}
    
    

/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