<!DOCTYPE math PUBLIC "-//W3C//DTD MathML 3.0//EN" "http://www.w3.org/TR/MathML3/dtd/mathml3.dtd">
<math xmlns="http://www.w3.org/1998/Math/MathML">
  <mstack>
    <mn>424</mn>
    <msrow> <mo>+</mo> <none/> <mn>33</mn> </msrow>
    <msline/>
  </mstack>
</math>