上下铺满自适应

如下代码:

<div class="" style="overflow: hidden;display: flex;flex-direction: column;height: 100%;background: #c0c0c0;">
<div class="" style="
    align-items: stretch;
    display: flex;
    flex: 1 0 auto;
    justify-content: flex-start;
    background: red;
">自适应的div</div>
<div style="margin-bottom: 0px;clear: both;font-size: 20px;width: 100%;background: blue;">固定div</div>
</div>