Varietas delectat 2

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        int szam;
        Scanner sc = new Scanner(System.in);
        while (true){
            boolean kül=true;
            szam = sc.nextInt();
            if (szam == 0)
                break;
            int[] numbers = new int[szam];
            for (int i = 0; i < szam; i++){
                numbers[i]=sc.nextInt();
            }
            for (int i = 0; i < szam; i++){
                for (int j = i + 1; j < szam; j++){
                    if (numbers[i] == numbers[j])
                        kül=false;
                }
            }
            if (kül == true)
                System.out.println("yes");
            else
                System.out.println("no");
        }
    }
}