import java.util.HashSet;
import java.util.Scanner;

/**
 * TITLE : Distinct or Not
 * URL : https://atcoder.jp/contests/abc154/tasks/abc154_c
 */
public class Main {

	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		HashSet<Integer> numberSet = new HashSet<Integer>();
		// N -1する必要があるかないか気をつけろ！
		for (int i = 0; i < N; i++) {
			if (!numberSet.add(sc.nextInt())) {
				System.out.println("NO");
				sc.close();
				return;
			}
		}
		System.out.println("YES");
		sc.close();
	}
}
/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