JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
<li>a</li>
<li>a</li>
<li>a</li>
<li>a</li>
</ul>

CSS

ul li {
  position: relative;
  line-height: 30px;
  height: 30px;
  list-style: none;
  width: 50px;
  display: inline-block;
  border-bottom: 1px solid green;
  text-align: center;
}
ul li:not(:last-child):not(:first-child) {
  margin: 0 20px;
}
ul li:last-child {
  margin-left: 20px;
}
ul li:first-child {
  margin-right: 20px;
}
ul li:not(:last-child):after {
  position: absolute;
  content: "-";
  right: -24px;
}