동일한 class의 요소를 한번에 여럿 생성하기
.class_name*n>.child_class_name
+ tab
<div class="class_name">
<div class="child_class_name"></div>
</div>
<div class="class_name">
<div class="child_class_name"></div>
</div>
<div class="class_name">
<div class="child_class_name"></div>
</div>