import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = Integer.parseInt(sc.next());
		String s  = "YES";
		Set<Integer> a = new HashSet<>();
		for(int i=0; i<N; i++) {
			int num = sc.nextInt();
			if(a.contains(num)){
				s = "NO";
				break;
			} else {
				a.add(num);
			}
		}
		sc.close();
		System.out.println(s);
	}

}
/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