<p>A magical string <code>s</code> consists of only <code>'1'</code> and <code>'2'</code> and obeys the following rules:</p> <ul> <li>The string s is magical because concatenating the number of contiguous occurrences of characters <code>'1'</code> and <code>'2'</code> generates the string <code>s</code> itself.</li> </ul> <p>The first few elements of <code>s</code> is <code>s = "1221121221221121122……"</code>. If we group the consecutive <code>1</code>'s and <code>2</code>'s in <code>s</code>, it will be <code>"1 22 11 2 1 22 1 22 11 2 11 22 ......"</code> and the occurrences of <code>1</code>'s or <code>2</code>'s in each group are <code>"1 2 2 1 1 2 1 2 2 1 2 2 ......"</code>. You can see that the occurrence sequence is <code>s</code> itself.</p> <p>Given an integer <code>n</code>, return the number of <code>1</code>'s in the first <code>n</code> number in the magical string <code>s</code>.</p> <p> </p> <p><strong class="example">Example 1:</strong></p> <pre> <strong>Input:</strong> n = 6 <strong>Output:</strong> 3 <strong>Explanation:</strong> The first 6 elements of magical string s is "122112" and it contains three 1's, so return 3. </pre> <p><strong class="example">Example 2:</strong></p> <pre> <strong>Input:</strong> n = 1 <strong>Output:</strong> 1 </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= n <= 10<sup>5</sup></code></li> </ul>