import java.util.*;

class Main {

	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		Map<Integer, Boolean> A = new TreeMap<Integer, Boolean>();
		boolean ans = true;
      	int N = sc.nextInt();
		for (int i = 0; i < N; i++) {
			int temp = sc.nextInt();
			if (!A.containsKey(temp)) {
				A.put(temp, true);
			} else {
				ans = false;
				break;
			}
		}
		System.out.println(ans ? "YES" : "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