Listitem is truly centered and the other items are in flow around it

Question

A list whereby one Listitem is truly centered and the other items are in flow around it. the centered Listitem can have a fixed width, the other items have the width of their content (text).

But without changes the HTML of the list. No extra containers or divs wrapped around it. how could I do this, if possible at all?

it might not be practical but I want to be able to do this as a challenge. I would like to live in a world where the HTML doesn't have to be changed to create a different design.

<ul>
  <li>size</li>
  <li>of</li>
  <li>fixed width</li>
  <li>size of content</li>
  <li>content</li>  
</ul>

ul{
  display: flex;
  list-style: none;
  width: 100%;