<!DOCTYPE html>
<style>
.container {
  float: left;
  margin: 20px 0;
  border: solid 2px;
  width: 100px;
}

.inflow {
  height: 40px;
}
</style>

<div class="container">
  <div class="inflow"></div>
  <div class="inflow" style="background: hotpink"></div>
  <div class="inflow"></div>
</div>

<div class="container">
  <div class="inflow"></div>
  <div class="inflow" style="background: hotpink"></div>
  <div class="inflow"></div>
</div>

<div class="container">
  <div class="inflow" style="background: hotpink"></div>
  <div class="inflow" style="background: green"></div>
</div>

<div class="container">
  <div style="height:100px; background:green;"></div>
</div>