import java.util.LinkedHashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		//━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
		int n = sc.nextInt();
		int[] numbers = new int[n];
		for (int i=0;i<n;i++) {
			numbers[i] = sc.nextInt();
		}
		int numbers_length = numbers.length;
		Set<Integer> linkedHashSet = new LinkedHashSet<Integer>();
		for (int i = 0; i < numbers.length; i++) {
			linkedHashSet.add(numbers[i]);
		}
		int numbers_length2 =linkedHashSet.size();
		
	if(numbers_length==numbers_length2){
		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