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

public class Main{

	public static void main(String[] args) {

		Scanner scanner = new Scanner(System.in);
		int n = Integer.parseInt(scanner.nextLine());
		String[] temp = scanner.nextLine().split(" ");
		Map<Long, Long> map = new HashMap<Long,Long>();

		for(int i = 0; i < n; i++) {

			Long tmp = Long.parseLong(temp[i]);

			if(!map.containsKey(tmp)) {

				map.put(tmp, (long) 1);

			}else {

				System.out.println("NO");
				return;

			}

		}

		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