```
% pandoc --number-sections
# One {-}

# Two

# Three {-}

# Four
^D
<h1 class="unnumbered" id="one">One</h1>
<h1 data-number="1" id="two"><span
class="header-section-number">1</span> Two</h1>
<h1 class="unnumbered" id="three">Three</h1>
<h1 data-number="2" id="four"><span
class="header-section-number">2</span> Four</h1>
```