Flex box generator

<div class="container">
    <div>1</div>
    <div>2</div>
    <div>3</div>
    <div>4</div>
    <div>5</div>
</div>

.container {
    border: 1px solid #ccc;
    min-height: 500px;
}
.container div {
    margin: 5px;
    text-align: center;
}
.container div:nth-child(1) {
    height: 70px;
    width: 70px;
    line-height: 70px;
    background-color: #444;
}
.container div:nth-child(2) {
    height: 60px;
    width: 60px;
    line-height: 60px;
    background-color: #666;
}
.container div:nth-child(3) {
    height: 50px;
    width: 50px;
    line-height: 50px;
    background-color: #999;
}
.container div:nth-child(4) {
    height: 40px;
    width: 40px;
    line-height: 40px;
    background-color: #ccc;
}
.container div:nth-child(5) {
    height: 30px;
    width: 30px;
    line-height: 30px;
    background-color: #ddd;
}