<ul class="flex-container">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>
  <li class="flex-item">4</li>
  <li class="flex-item">5</li>
</ul>

.flex-container {
  padding: 0;
  margin: 0;
  list-style: none;
  
  -ms-box-orient: horizontal;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -moz-flex;
  display: -webkit-flex;
  display: flex;
  
  -webkit-flex-flow: row wrap;
  flex-flow: row wrap;
}

.flex-item:nth-of-type(1) { order: 3; }
.flex-item:nth-of-type(2) { order: 4; }
.flex-item:nth-of-type(3) { order: 1; }
.flex-item:nth-of-type(4) { order: 5; }
.flex-item:nth-of-type(5) { order: 2; }

.flex-item {
  background: tomato;
  padding: 5px;
  width: 100px;
  height: 100px;
  margin: 5px;
  
  line-height: 100px;
  color: white;
  font-weight: bold;
  font-size: 2em;
  text-align: center;
}