display:flex属性 justify-content: space-between换行后的排版问题

<style>
.wrap {
	width: 400px;
	display:flex;  /*弹性盒子*/
	justify-content: space-between;  /*两端对齐，子元素之间有间隙*/
	flex-flow: row wrap;/*子元素溢出父容器时换行*/
}
span {width: 100px;background-color: green;color:#fff;border-radius: 5px;margin-top: 10px;padding: 10px;}
</style>

<div class="wrap">
	<span>11</span>
	<span>22</span>
	<span>33</span>
	<span>44</span>
	<span>55</span>
</div>