bootstrap-select in nav

HTML

<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/js/bootstrap-select.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/css/bootstrap-select.css">
<select class="selectpicker Categoria" multiple="">
    <option selected>A1</option>
    <option selected>A2</option>
    <option>A3</option>
    <option>A4</option>
</select>
<input type="text" class="ChangeCategory" name="ChangeCategory">

CSS

body {
  padding: 20px;  
}

JavaScript

$('select').selectpicker();

$(".Categoria").change(function() {
  f2();
});

var f2 = function(){
  $('.ChangeCategory').val($(".Categoria").val());
}
f2();