代码编辑器：
x
1
<h1>This is the main heading</h1>2
<p>Some initial text</p>3
<h2>This is a level 2 heading</h2>4
<p>This is some text. </p>5
<h3>This is a level 3 heading</h3>6
<p>This is some text.</p>7
<h3>This is a level 3 heading</h3>8
<p>This is some text.</p>9