
import java.util.*;
import java.lang.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) {
        //コード
        Scanner scanner = new Scanner(System.in);
        Integer n = Integer.parseInt(scanner.next());

        List<Long> listA = new ArrayList<Long>();

        Integer[] a = new Integer[n];
        for(int i = 0; i < a.length; i++) {
            listA.add(scanner.nextLong());
            //a[i] = Integer.parseInt(scanner.next());
        }

        List<Long> listB = new ArrayList<Long>(new HashSet<>(listA));

        if(listA.size() == listB.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