<!doctype html>
<html>
<head>
<meta charset="utf-8">
<script>
addEventListener("DOMContentLoaded", () => {
  getSelection().collapse(document.querySelector("ol"), 0);
  document.execCommand("delete");
});
</script>
</head>
<body>
<details open contenteditable>
<map>
<video>
<source></source>
<ol>
<li>a</li>
</ol>
</video>
</map>
</details>
</body>
</html>
