import java.util.*;

class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        int[] num = new int[n];
        for(int i = 0;i < n;i++){
            num[i] = sc.nextInt();
        }
        Arrays.sort(num);
        for(int i = 0;i < n-1;i++){
            if(num[i]==num[i+1]){
                System.out.println("NO");
                return;
            }
        }
        
        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