How can I show three columns per row?

body>div {
  background: #aaa;
  display: flex;
  flex-wrap: wrap;
}

body>div>div {
  flex-grow: 1;
  width: 33%;
  height: 100px;
}

body>div>div:nth-child(even) {
  background: #23a;
}

body>div>div:nth-child(odd) {
  background: #49b;
}

<div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
  <div></div>
</div>