import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		// 自分の得意な言語で
		// Let's チャレンジ！！

		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		sc.nextLine();
		String strLine = sc.nextLine();
		String[] strArr = strLine.split(" ");

		String re = "YES";
		List l = Arrays.asList(strArr);
		Collections.sort(l);

		for (int i = 0; i < l.size() - 1; i++) {
			if (l.get(i).equals(l.get(i + 1))) {
				re = "NO";
				break;
			}
		}

		System.out.println(re);

	}

}
/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