<p>Given an integer <code>n</code>, add a dot (".") as the thousands separator and return it in string format.</p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> n = 987 <strong>Output:</strong> "987" </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> n = 1234 <strong>Output:</strong> "1.234" </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>0 <= n <= 2<sup>31</sup> - 1</code></li> </ul>