body {
    height: 100rem;
}

table,
tr {
    border: 1px solid #000000;
}

td,
th {
    padding: 0.1rem 0.5rem;
}

th,
tr:nth-of-type(8n + 6),
tr:nth-of-type(8n + 7),
tr:nth-of-type(8n + 8),
tr:nth-of-type(8n + 9) {
    background-color: #cccccc;
}