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

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashSet<Long> list = new HashSet<Long>();
		boolean check = true;
		long in = 0;

		for(int i = 0;i < n;i++) {
			in = scan.nextLong();
			if(list.contains(in)) {
				check = false;
			}
			list.add(in);
		}

		if(!check) {
			System.out.println("NO");
		}else {
			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