<p>We call a positive integer <strong>special</strong> if all of its digits are <strong>distinct</strong>.</p> <p>Given a <strong>positive</strong> integer <code>n</code>, return <em>the number of special integers that belong to the interval </em><code>[1, n]</code>.</p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> n = 20 <strong>Output:</strong> 19 <strong>Explanation:</strong> All the integers from 1 to 20, except 11, are special. Thus, there are 19 special integers. </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> n = 5 <strong>Output:</strong> 5 <strong>Explanation:</strong> All the integers from 1 to 5 are special. </pre> <p><strong>Example 3:</strong></p> <pre> <strong>Input:</strong> n = 135 <strong>Output:</strong> 110 <strong>Explanation:</strong> There are 110 integers from 1 to 135 that are special. Some of the integers that are not special are: 22, 114, and 131.</pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= n <= 2 * 10<sup>9</sup></code></li> </ul>