import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;

public class Main {
	public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Random rand = new Random();
        //ArrayList<Integer> list;
        List<Integer> list = new ArrayList<>(200000);
        
        int number = sc.nextInt();
        for(int i = 0; i < number ; i++){
            list.add(sc.nextInt());
        }

        Collections.sort(list);
        int count = 0;
        for(int i = 0; i < number - 1 ; i++){
            if(list.get(i).equals(list.get(i+1))){
                count++;
            }else{}
        }
        //System.out.println(list);

        if(count == 0){
            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