import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;
 
public class Main {
 
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Set<Integer> c = new HashSet<>();
		for(int i=0;i<n;i++){
			c.add(sc.nextInt());
		}
		sc.close();
		if(n==c.size()){
			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