import java.util.*;
class Main{
	public static void main(String args[]){
      Scanner sc = new Scanner(System.in);
      int a = sc.nextInt();
      Set t = new HashSet<Integer>();
      boolean ok = true;
      for(int i = 0;i<a;i++){
        t.add(sc.nextInt());
      }

      if(t.size()==a)System.out.println("YES");
      else System.out.println("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