import java.util.Scanner;
import java.util.Arrays;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i = 0 ; i < n ; i++) {
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        boolean che = false;
        for(int i = 0 ; i < n - 1 && che == false ; i++ ){
            if(a[i] == a[i + 1]){
                che = true;
            }
        }
        if(che == false){
            System.out.println("YES");
        }else{
            System.out.println("NO");
        }
        sc.close();
    }
}
/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