<p>You are given a string <code>s</code> and an integer <code>k</code>. You can choose one of the first <code>k</code> letters of <code>s</code> and append it at the end of the string..</p> <p>Return <em>the lexicographically smallest string you could have after applying the mentioned step any number of moves</em>.</p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> s = "cba", k = 1 <strong>Output:</strong> "acb" <strong>Explanation:</strong> In the first move, we move the 1<sup>st</sup> character 'c' to the end, obtaining the string "bac". In the second move, we move the 1<sup>st</sup> character 'b' to the end, obtaining the final result "acb". </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> s = "baaca", k = 3 <strong>Output:</strong> "aaabc" <strong>Explanation:</strong> In the first move, we move the 1<sup>st</sup> character 'b' to the end, obtaining the string "aacab". In the second move, we move the 3<sup>rd</sup> character 'c' to the end, obtaining the final result "aaabc". </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= k <= s.length <= 1000</code></li> <li><code>s</code> consist of lowercase English letters.</li> </ul>