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

public class Main {
  	public static void main(String[] args){

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		boolean ans = true;

		HashSet<Integer> hs = new HashSet<>();

		for(int i=0;i<N;i++){
			int ai = sc.nextInt();

			if(hs.contains(ai)){
				ans = false;
				break;
			}

			hs.add(ai);
		}

		if(ans){
			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