How to add line-separator in navbar? - twitter-bootstrap-3

Question

I need to add separators between the links. Took navbar from boostrap3 components. Tried to use border-left, but failed. Broke my brain with this simple problem. Would be very thankful for any help.
.navbar-default {
z-index: 2;
text-transform: uppercase;
background-color: #cb5a3d;
}
.navbar-default .navbar-nav li > a {
margin-right: 100px;
padding: 25px 0;
color: #FFFFFF;
font-family: "FiraSans-bold", sans-serif;
}
.navbar-default .navbar-nav li:first-child {
margin-left: 100px;
<nav class="navbar navbar-default">
<!-- Brand and toggle get grouped for better mobile display -->
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
</div>
<!-- Collect the nav links, forms, and other content for toggling -->
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav">
<li>о компании
</li>
<li>услуги
</li>
<li>новости
</li>
<li>полезная информация
</li>
<li>контакты
</li>
</ul>
</div>
<!-- end navbar-collapse -->
</nav>
<!-- end navbar -->