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

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int in_num = sc.nextInt();
        Map<Integer,Integer> m = new HashMap<>();
        for(int i = 0; i < in_num ;i++){
            int a = sc.nextInt();
            if(m.containsKey(a)){
                System.out.println("NO");
                return;
            }else{
                m.put(a, null);
            }
        }
        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