import java.util.HashMap;
import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		HashMap<String,String> map = new HashMap<String,String>();

		Scanner scan = new Scanner(System.in);
		String str = scan.nextLine();
		int n = Integer.parseInt(str);

		str = scan.nextLine();
		String[] substr = str.split(" ", 0);
		String ans = "YES";
		for (int i=0; i<n; i++) {
			if (map.containsKey(substr[i])) {
				ans = "NO";
				break;
			}  else {
				map.put(substr[i], "1");
			}
		}

		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