<style>
	.demo_css_sprt, .demo_css_sprt div	{
		border: 1px dotted red;
		padding: 1em;
	}
	.demo_css_sprt div	{
		margin: 1em 0;
	}
	.demo_css_sprt p	{
		border: 1px dashed blue;
		padding: 1em;
	}
	.demo_css_sprt div p:only-of-type	{
		background: lavender;
	}
</style>
<div class="demo_css_sprt">
	要素1
	<div>要素2
		<p>要素3</p>
		<div>要素4</div>
	</div>
	<div>要素5
		<p>要素6</p>
		<p>要素7</p>
	</div>
</div>