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

public class Main {
 
	public static void main(String[] args) {
 
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		Set<Long> numSet = new HashSet<>();
		boolean hasSame = false;
		for(int i = 0; i < n; i++) {
			Long num = sc.nextLong();
			if(numSet.contains(num)) {
				hasSame = true;
				break;
			}else {
				numSet.add(num);
			}
		}
		
		System.out.println(hasSame ? "NO" : "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