How to make the float left and float right on the same line?

The Problem:

     **The left part** (#nav ul li) which float: left
     and **the right part** (#nav .search) which float: right
            **are not in a line**.

it should be like this:

but mine:

The HTML:

<div id="nav">
   <ul>
     <li><a href="#">Home</a></li>
     <li><a href="#">Portfolio</a></li>
     <li><a href="#">Blog</a></li>
     <li><a href="#">Contact</a></li>
   </ul>
   <div class="search">
     <input type="text" name="search" id="search" value="search">
   </div>       

The CSS:

#nav ul li{
float: left;
list-style: none;
margin: 0 20px;
}

#nav .search{
float: right;
}

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My Solutions:

Solution 1: Use bootsrap to build layout instead of doing it on my own, i use it on the footer, and it's perfectly on the same line! Yet I still don't know how it works

Solution 2: I use margin-top: -20px to pull the search box up, but I don't think it is a good practice.

Any one can help? Many thanks!

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