How to select a selector with CSS?

Question

css

There is this HTML:

<div class="btnGroup">
    <input class="btn__input">
    <label class="btn"></label>
    <input class="btn__input">
    <label class="btn"></label>
    <input class="btn__input">
    <label class="btn"></label>
</div>

How to use CSS to select the first label through btnGroup? You can't use the label tag, because we use the BEM methodology (today it's a label, but tomorrow it can be a div or something else)
ps The task is very simple - remove the rounding from the buttons in the group that are between the first and last buttons.

Answer 1

fix quotes)
.btnGroup .btn:first-of-type