import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        int count = scanner.nextInt();
        scanner.nextLine();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < count; i++){
            list.add(scanner.nextInt());
        }
        if(list.stream().distinct().collect(Collectors.toList()).size() == list.size()){
            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