.parent article {
    border:2px solid #999;
    padding:10px;
    box-sizing: border-box;
}

.parent {
    border:2px solid #000;
    display:flex;
    padding:4px;
}
.parent.childrenfixe article{
    width:25%;
}

.parent.nowrap {
    flex-wrap: nowrap;
}
.parent.wrap {
    flex-wrap: wrap;
}
.parent.justify-content{
    justify-content:space-between;
}
.parent .element2 {
order:-1;
}
.parent .element4 {
  flex-grow: 4;
}