If the following CSS was applied, which lines would be affected?

example-3.css

li:nth-child(3n + 1) {
  background: red;
}

example-3.html

<div class="shopping list">
  <ul>
    <li>Ham</li>
    <li>Eggs</li>
    <li>Cheese</li>
    <li>Cups</li>
    <li>Wool Blanket</li>
    <li>Veggies</li>
    <li>Steak</li>
    <li>Birthday Cake</li>
    <li>Chicken</li>
    <li>Ice Cream</li>
    <li>Nacho Chips</li>
    <li>Salso</li>
  </ul>
</div>