Flexbox container and overflowing flex children?

Question

I've made this : http://codepen.io/Canapin/pen/NNwMeq

#a {
  height: 150px;
  border: 1px solid black;
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  position: absolute;
}

.b {
  background: yellow;
  height: 50px;
  border: 1px solid black;
  width: 50px;
  margin: 10px;
}

<div id="a">
  <div class="b">1</div>
  <div class="b">2</div>
  <div class="b">3</div>
  <div class="b">4</div>
  <div class="b">5</div>
</div>

Is there any way to make the container having a flexible width according to its content, like an inline block ?

edit : this should be the expected result :