import java.util.*;

public class Main {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++)
			arr[i] = sc.nextInt();
		Arrays.sort(arr);
		Boolean flag = true;
		for (int i = 0; i < n-1 && flag; i++) {
			if (arr[i] == arr[i+1])
				flag = false;
		}			
		if (flag)
			System.out.print("YES");
		else
			System.out.print("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