tyle="margin-top: calc(140px / 3)"/>
    </div>
    <div class="flexbox">
      <div class="c" style="margin-top: 10px"
           /><div class="b" style="margin-top: 10px"
           /><div class="a" style="margin-top: 10px"/>
    </div>

    <!-- left -->
    <div class="flexbox">
      <div class="a"/>
    </div>
    <div class="flexbox">
      <div class="b"/><div class="a"/>
    </div>
    <div class="flexbox">
      <div class="c"/><div class="b"/><div class="a"/>
    </div>

    <!-- right -->
    <d