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