如何在导航中居中显示右边框？

<div class="navigation">
  <ul>
    <li><a href="#">首页</a></li>
    <li><a href="#">产品</a></li>
    <li><a href="#">服务</a></li>
    <li><a href="#">关于我们</a></li>
  </ul>
</div>

.navigation {
  width: 600px;
  margin: 0 auto;
}

.navigation ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.navigation ul li {
  display: inline-block;
}

.navigation ul li a {
  display: block;
  padding: 10px;
  text-decoration: none;
}

.navigation ul li a::after {
  content: "";
  display: block;
  width: 1px;
  height: 100%;
  background-color: #000;
  margin-left: 10px;
}