import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Collections;
import java.util.TreeSet;

public class Main {
	public static void main(String[] args) throws IOException {
		TreeSet<String> input = new TreeSet<String>();
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int num = Integer.parseInt(br.readLine());
		Collections.addAll(input, br.readLine().split(" "));
		System.out.println(input.size() != num ? "NO" : "YES");
	}

}

/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