Add class is not working

Add class is not working

Hello friends i have three submit buttons.
and i want to add the class1 on the button which has the text 'a' by clicking on the button which has text
'Click me to add'.
But when i click this button it gives nothing.
Please help!

HtML--

<div>
    <div>
        <input type="submit" name="name" value="a" />
        <input type="submit" name="name" value="b" />
        <input type="submit" name="name" value="CLick me to add" id="Sub" />
    </div>
</div>

CSS--

  <style type="text/css">
         
        input[type=submit] {
            width: 60px;
            height: 40px;
            background-color:rgba(40, 35, 35, 0.84);
            font-size:large;
            color:white;
        }
        .class1 {
            background-color:white;
        }
    </style>

Javascript--

<script type="text/javascript" src="jquery-1.11.1.js"></script>
 <script type="text/javascript">
        $(document).ready(function () {
            $("#Sub").click(function(){
                var Mybutton = $(":submit").filter(function () {
                    if ($(this).val()=='a') {
                        return this;
                    }
                });                
                    $(Mybutton).addClass("class1");                             
            });
        });
    </script>