import java.util.*;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	HashMap<Integer, Integer> dict = new HashMap<>();
		int N = sc.nextInt();      	 
      	int Current;
      	for(int i=0 ;i<N;i++)
        {
          	Current=sc.nextInt();
          	if(dict.containsKey(Current))
            {
          		System.out.println("NO");
              	System.exit(0);
            }
          	else 
            {
              	dict.put(Current, 1);              	
            }
        }
      	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