body {
    display: grid;
    font-family: sans-serif;
    grid-template-areas:
        "header header header"
        "sidebar main ."
        "footer footer footer";
    height: 100vh;
    margin: 0;
}

header {
    grid-area: header;
}

footer {
    grid-area: "footer";
}

main {
    grid-area: main;
    text-align: center;
}