我在模态对话框中使用输入组.按钮比其他元素少1px.我该如何修复它,更不用说为什么我有这个bug呢？我使用Bootstrap 3
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<div class="buttons input-group col-sm-offset-1 col-sm-9">
<input type="number" min="1" value="1" class="form-control" />
<span class="input-group-addon">ks</span>
<span class="input-group-btn">
<button type="button" class="btn btn-default glyphicon glyphicon-remove color-red"/>
</span>
</div>