<p>An integer has <strong>monotone increasing digits</strong> if and only if each pair of adjacent digits <code>x</code> and <code>y</code> satisfy <code>x <= y</code>.</p>
<p>Given an integer <code>n</code>, return <em>the largest number that is less than or equal to </em><code>n</code><em> with <strong>monotone increasing digits</strong></em>.</p>