title: how to make a new line in a jupyter markdown cell
body: <p><code>md
  $S$: a set of shops
  $I$: a set of items M wants to get
  </code></p>
  
  <p>I'd like to make a new line between this two sentences.
  We usually put " (space)" after the first sentence before a new line, but it doesn't work in Jupyter.</p>
  
  <p>How can I do this? Should I put "enter" twice after the first sentence?</p>