css: slightly angled border radius
<p>I wanna create a sticky note with html and css.
my code is like this:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-css lang-css prettyprint-override"><code>.div{
 margin:50px;
 position:relative;
}
.box {
background: #ff1;
height: 178px;
width: 409px;
margin: 25px;
/*padding: 20px;*/
position: relative;
overflow: hidden;

border-left: 0px;
border-top-left-radius:70px;
border-bottom-right-radius:30px
}
.box:before {
content: "";
display: block;
background: #fff;
position: absolute;
top: -38px;
left: -268px;
width: 310px;
height: 248px;
border-bottom-right-radius: 70px;
padding:0px;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="div"&gt;
&lt;div class="box"&gt;&lt;/div&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>

<p>My problem is the right-button 
It is quite curves. But I would be slightly angled. Like what you see in the image.
Can any body help me please? Thanks.</p>

<p><a href="https://i.stack.imgur.com/TMkSr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TMkSr.png" alt="enter image description here"></a></p>