<div id="parent">
<div class="odd"></div>
<div class="even"></div>
<div class="odd"></div>
<div class="even"></div>
<div class="odd"></div>
<div class="even"></div>
<div class="odd"></div>
<div class="even"></div>
</div>
.wrapper {
width: 150px;
}
.wrapper {
width: 450px;
display: flex;
flex-direction: column;
height: 70px;
flex-wrap: wrap;
}
.wrapper {
width: 450px;
display: flex;
flex-direction: row;
flex-wrap: wrap;
}
.block:nth-child(odd) {
order: 1;
}
.block:nth-child(even) {
order: 2;
}