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