JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container clearfix">
  <div class="block fl">1</div>
  <div class="block fl">2</div>
  <div class="block fr">3</div>
  <div class="block fl">4</div>
  <div class="block fl">5</div>
  <div class="block fl">6</div>
  <div class="block fr">7</div>
  <div class="block fl">8</div>
  <div class="block fl">9</div>
  <div class="block fl">10</div>
  <div class="block fr">11</div>
  <div class="block fl">12</div>
  <div class="block fl">13</div>
  <div class="block fl">14</div>
</div>

CSS

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.clearfix:after {
  content: '';
  dispaly: table;
  clear: both;
}

.fl {
  float: left;
}

.fr {
  float: right;
}

.block {
  width: 50%;
  padding: 15px;
  background: #eee;
  border: 1px solid #333;
  text-align: center;
}