import java.util.*;
class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        Set<Integer> as = new HashSet<Integer>();
        String ans = "YES";
        for(int i = 0 ;i<a.length;i++){
            a[i] = sc.nextInt();
            as.add(a[i]);
        }
        if(a.length!=as.size()){
            ans = "NO";
        }
        System.out.println(ans);
    }
}
/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