<p>Given two strings <code>str1</code> and <code>str2</code>, return <em>the shortest string that has both </em><code>str1</code><em> and </em><code>str2</code><em> as <strong>subsequences</strong></em>. If there are multiple valid strings, return <strong>any</strong> of them.</p> <p>A string <code>s</code> is a <strong>subsequence</strong> of string <code>t</code> if deleting some number of characters from <code>t</code> (possibly <code>0</code>) results in the string <code>s</code>.</p> <p> </p> <p><strong class="example">Example 1:</strong></p> <pre> <strong>Input:</strong> str1 = "abac", str2 = "cab" <strong>Output:</strong> "cabac" <strong>Explanation:</strong> str1 = "abac" is a subsequence of "cabac" because we can delete the first "c". str2 = "cab" is a subsequence of "cabac" because we can delete the last "ac". The answer provided is the shortest such string that satisfies these properties. </pre> <p><strong class="example">Example 2:</strong></p> <pre> <strong>Input:</strong> str1 = "aaaaaaaa", str2 = "aaaaaaaa" <strong>Output:</strong> "aaaaaaaa" </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= str1.length, str2.length <= 1000</code></li> <li><code>str1</code> and <code>str2</code> consist of lowercase English letters.</li> </ul>