<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
body,
html {
margin: 0;
padding: 0;
height: 100%
}
.container {
display: flex;
}
.left {
width: 400px;
display: flex;
flex-direction: column;
background-color: aquamarine;
}
.title {
height: 300px;
background-color: darkgoldenrod;
}
.content {
flex: 1;
overflow: auto;
}
ul li {
padding: 300px 0;
}
.right {
flex: 1;
}
</style>
</head>
<body>
<div class="container">
<div class="left">
<div class="title">123</div>
<div class="content">
<ul>
<li>123</li>
<li>123</li>
<li>123</li>
<li>123</li>
<li>123</li>
<li>123</li>
</ul>
</div>
</div>
<div class="right">right</div>
</div>
</body>
</html> 
Why doesn"t the div.content on the left appear scroll bar? Is this the wrong way for flex to use it?