import java.util.*;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt();
		int[] num = new int[n];
		int chk = 0;
		
		for (int i = 0; i < n; i++) {
			num[i] = sc.nextInt();
		}
		
		Arrays.sort(num);
		

		for (int i = 0; i < n - 1; i++) {
			if (num[i] == num[i + 1]) {
				System.out.println("NO");
				chk++;
				break;
			}
		}
		
		if (chk == 0) {
			System.out.println("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