import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {

//    	File file = new File("test.txt");
//    	Scanner sc = new Scanner(file);
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	Map<Integer, Boolean> map = new HashMap<>();
    	for(int i = 0; i < n; i++){
    		int a  = sc.nextInt();
    		if(null != map.get(a)){
    			System.out.println("NO");
    			sc.close();
    			return;
    		}else{
    			map.put(a, true);;
    		}
    	}
    	sc.close();
    	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