
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());

		Set<Integer> set = new HashSet<Integer>();
		for(int i = 0 ;i < n ;i++) {
			int a = Integer.parseInt(sc.next());
			set.add(a);
		}
		
		if(set.size() == n) {
			System.out.println("YES");
		}
		else {
			System.out.println("NO");
		}
	}

}

/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