How to draw this shape with css?

Please help me to write css to something like this happened beautifully.
The Internets couldn't find ready ugly options, even the base is nothing to take.
In my case it will be 1 box, telephone number, and a submit button.
Here is a skeleton.
<form class="form-wrapper cf">
[tel* tel-181 placeholder "Your phone number"]
[submit "call!"] 

June 7th 19 at 15:37
1 answer
June 7th 19 at 15:39

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