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

/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