How do I get alternating values for channel entries?

I am trying to figure out how would I go about getting the result of my channel entries to render with alternating values on the html structure I have below;

<ol class=”portfolio-list”> {exp:channel:entries channel="portfolio" cache="yes"}<li data-aos=”fade-CHANGINGVALUE”> _ <div class=”portfolio-thumb”>_ {project-banner}_ </div>_ <div class=”portfolio-summary”>_ <div class=”portfolio-summary-title”>{title}</div>_ </div>_ </li> {/exp:channel:entries}
</ol>

Above, where I have CHANGINGVALUE, I need it to alternate from left/right as it goes down a list. I feel like I’m close and feel like there is something super easy I am missing … Asking for the help from the community! Any help is greatly appreciated.