In this Fiddle, how can I reduce the space between the individual content(the 1,2,3,4) and its border. I'm kinda new to Flexbox, and I don't know if there is an easy fix to this.

Here is what I mean(more specifically)

<https://ibb.co/z73dJ4m>

versus

<https://ibb.co/pzwhVB5>

Thanks

JS Fiddle: <https://jsfiddle.net/Ragingfury/0nrq94jt/2/>

```css
.a{
  display: flex;
  justify-content: space-around;
  align-items: center;
  flex-flow:row wrap;
  text-align:center;
}
.b{
flex:40%;
margin:20px;
border:1px solid blue;
}
```

```html
<div class="a">

  <div class="b">
    1
  </div>
  <div class="b">
    2
  </div>
  <div class="b">
    3
  </div>
  <div class="b">
    4
  </div>

</div>
```