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

public class Main {
	public static void main(String[] args){
		try(Scanner sc = new Scanner(System.in)) {
		
			int n = sc.nextInt();
			
			Set<Integer> countSet = new HashSet<>();
			boolean isDuplicated = false;
			
			for(int i = 0 ; i < n ; i++ ) {
				
				int v = sc.nextInt();
				
				if (countSet.contains(v)) {
					isDuplicated = true;
				}
				countSet.add(v);
			}
			
			if ( isDuplicated ) {
				System.out.println("NO");
			}
			else {
				System.out.println("YES");
			}
		}
	}
}
/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