<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div class="container">
<div class="row">
<form class="needs-validation" novalidate>
<div class="form-row">
<div class="col-md-4 mb-3">
<label for="validationCustom01">First name</label>
<input type="text" class="form-control" id="validationCustom01" placeholder="First name" value="Mark" required>
<div class="valid-feedback">
Looks good!
</div>
</div>
<div class="col-md-4 mb-3">
<label for="validationCustom02">Last name</label>
<input type="text" class="form-control" id="validationCustom02" placeholder="Last name" value="Otto" required>
<div class="valid-feedback">
Looks good!
</div>
</div>
<div class="col-md-4 mb-3">
<label for="validationCustomUsername">Username</label>
<div class="input-group">
<div class="input-group-prepend">
<span class="input-group-text" id="inputGroupPrepend">@</span>
</div>
<input type="text" class="form-control" id="validationCustomUsername" placeholder="Username" aria-describedby="inputGroupPrepend" required>
<div class="invalid-feedback">
Please choose a username.
</div>
</div>
</div>
</div>
<div class="form-row">
