CSS------制作一个带+-的input框

<div style="font-size:36px;margin-top:30px">
<div style="display:inline;background-color:#f9f9f9;padding-left:5px;padding-right:5px;border:1px solid #aaa">-</div>
<input type="number" value="1" readonly style="text-align:center;font-size:25px;height:45px;margin-top:-6px;width:100px;border-left:0px;border-right:0px;border-bottom:1px solid #aaa"/>
<div style="display:inline;background-color:#f9f9f9;border:1px solid #aaa">+</div>
</div>