html, body {
    margin: 0;
    padding: 0;
    height: 100%;
    width: 100%;
}

.parent {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr 1fr;
    grid-template-rows: 1fr 3fr 1fr;
    grid-column-gap: 0%;
    grid-row-gap: 0%;
    }
    
    .header {
        grid-area: 1 / 1 / 2 / 6;
    }

    .leftBox {
        grid-area: 2 / 1 / 5 / 3;
    }

    .rightBox {
        grid-area: 2 / 4 / 5 / 6;
    }

    .footer {
        grid-area: 5 / 1 / 6 / 6;
    }