import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        HashMap<Integer,Integer> hash = new HashMap<>();
        int n = sc.nextInt();
        for (int i=0;i<n;i++){
            int j = sc.nextInt();
            if (hash.containsKey(j))hash.put(j,2);
            else hash.put(j,1);
        }
        boolean b = true;
        for (int a : hash.values()){
            if (a > 1) {
                b = false;
                break;
            }
        }
        if (b)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