Validation failed (numeric string is expected)

    <div>
        <h2>Validation Failed</h2>
        <p>Numeric string is expected.</p>
        <h3>Examples:</h3>
        <ul>
            <li>
                <p>Input: "12345"</p>
                <p>Expected: Valid</p>
            </li>
            <li>
                <p>Input: "12a3b45"</p>
                <p>Expected: Invalid</p>
            </li>
            <li>
                <p>Input: "abcde"</p>
                <p>Expected: Invalid</p>
            </li>
        </ul>
    </div>