import java.util.*;
 
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    Set<Integer> hash_set = new HashSet<Integer>();
    for (int i = 0; i < N; i++) {
       hash_set.add((Integer)sc.nextInt());
    }
    if(hash_set.size()  ==(Integer)N){
      System.out.print("YES");
    }else{
    System.out.print("NO");
    }
}  
}
/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