import java.util.*;
public class Main{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
  int num = Integer.parseInt(sc.next());
  int[] array = new int[num];
  String ans = "YES";
  for (int i = 0; i < num; i++){
  array[i] = Integer.parseInt(sc.next());
  }
  Arrays.sort(array);
  for (int i = 1; i <num; i++){
  	if(array[i-1] == array[i]){
    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