import java.util.HashSet;
import java.util.Scanner;
 
public class Main {
 
	public static void main(String[] args) {
 
		int n;
 
		Scanner sc = new Scanner(System.in);
 
		n = sc.nextInt();
 
		HashSet<Integer> hs = new HashSet<Integer>();
 
		boolean flag = false;
		String ans = "";
 
		for (int i = 1; i <= n; i++) {
 
			int tmp = sc.nextInt();
 
			if (hs.contains(tmp)) {
				flag = true;
				break;
			} else {
				hs.add(tmp);
			}
		}
 
		if (flag) {
			ans = "NO";
		} else {
			ans = "YES";
		}
 
		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