Correct html with missing tag

Currently I am working on a solution to correct HTML. In our solution we have a rich text editor where we want to correct the HTML when the user forgets a <p> element, which happens a lot.

var input = new StringBuilder();
input.AppendLine("<h2>title1</h2>");
input.AppendLine("text");
input.AppendLine("<h2>title2</h2>");
input.AppendLine("<p>paragraph</p>");

var expected = new StringBuilder();
expected.AppendLine("<h2>title1</h2>");
expected.AppendLine("<p>text</p>");
expected.AppendLine("<h2>title2</h2>");
expected.AppendLine("<p>paragraph</p>");

Assert.AreEqual(expected.ToString(), input.DoSomething());

Is there something in the HTML agility pack? Of is there another solution?