import java.util.*;
public class Main
{
  public static void main(String args[])
  {
    Scanner in=new Scanner(System.in);
    HashSet<Integer> set=new HashSet<>();
    int n=in.nextInt();
    int arr[]=new int[n];
    for(int i=0;i<n;i++)
    {
      arr[i]=in.nextInt();
      set.add(arr[i]);
    }
    if(set.size()==n)
    {
      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