import java.util.*;

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

        for (int i = 0; i < N; i++) ts.add(Integer.parseInt(scanner.next()));

        if(N == ts.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