html, body {
    height: 100%;
}
body {
    margin: 0;
    background-color: #f2f2f2;
}
.flex-container {
    height: 100%;
    padding: 0;
    margin: 0;
    display: -webkit-box;
    display: -moz-box;
    display: -ms-flexbox;
    display: -webkit-flex;
    display: flex;
    align-items: center;
    justify-content: center;
}
.row {
    width: auto;
}