How to keep the post class not change in the loop?

The default post class is
<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>

But I want to keep the class not change in the loop,
I mean on the homepage, I want to list 10 posts, each post has different,

<h3>latest posts</h3>
<article id="post-<?php the_ID(); ?>" class="post-1">

<article id="post-<?php the_ID(); ?>" class="post-2">

<article id="post-<?php the_ID(); ?>" class="post-3">

<article id="post-<?php the_ID(); ?>" class="post-4">

<article id="post-<?php the_ID(); ?>" class="post-5">

The most recent post always has the class-1, and the previous one always has the class-2

I don’t know how to write the php, can you help me? Thank you.