import java.util.*;
public class Main {
	public static void main(String[] args){
      	
		Scanner sc = new Scanner(System.in);
		//String word_before = sc.next();
		int N = sc.nextInt();
		int num_arr[] = new int[N];
		boolean flag = true;
		for (int i = 0; i < num_arr.length; i++) {
			num_arr[i] = sc.nextInt();
		}
		Arrays.sort(num_arr);
		for (int i = 0; i < num_arr.length-1; i++) {
			if(num_arr[i] ==num_arr[i+1]){
				flag = false;
				break;
			}
		}
		if (flag) {
			System.out.println("YES");
		} else {
			System.out.println("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