<p>There are <code>n</code> projects numbered from <code>0</code> to <code>n - 1</code>. You are given an integer array <code>milestones</code> where each <code>milestones[i]</code> denotes the number of milestones the <code>i<sup>th</sup></code> project has.</p>

<p>You can work on the projects following these two rules:</p>

<ul>
	<li>Every week, you will finish <strong>exactly one</strong> milestone of <strong>one</strong> project. You&nbsp;<strong>must</strong>&nbsp;work every week.</li>
	<li>You <strong>cannot</strong> work on two milestones from the same project for two <strong>consecutive</strong> weeks.</li>
</ul>

<p>Once all the milestones of all the projects are finished, or if the only milestones that you can work on will cause you to violate the above rules, you will <strong>stop working</strong>. Note that you may not be able to finish every project&#39;s milestones due to these constraints.</p>

<p>Return <em>the <strong>maximum</strong> number of weeks you would be able to work on the projects without violating the rules mentioned above</em>.</p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> milestones = [1,2,3]
<strong>Output:</strong> 6
<strong>Explanation:</strong> One possible scenario is:
​​​​- During the 1<sup>st</sup> week, you will work on a milestone of project 0.
- During the 2<sup>nd</sup> week, you will work on a milestone of project 2.
- During the 3<sup>rd</sup> week, you will work on a milestone of project 1.
- During the 4<sup>th</sup> week, you will work on a milestone of project 2.
- During the 5<sup>th</sup> week, you will work on a milestone of project 1.
- During the 6<sup>th</sup> week, you will work on a milestone of project 2.
The total number of weeks is 6.
</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> milestones = [5,2,1]
<strong>Output:</strong> 7
<strong>Explanation:</strong> One possible scenario is:
- During the 1<sup>st</sup> week, you will work on a milestone of project 0.
- During the 2<sup>nd</sup> week, you will work on a milestone of project 1.
- During the 3<sup>rd</sup> week, you will work on a milestone of project 0.
- During the 4<sup>th</sup> week, you will work on a milestone of project 1.
- During the 5<sup>th</sup> week, you will work on a milestone of project 0.
- During the 6<sup>th</sup> week, you will work on a milestone of project 2.
- During the 7<sup>th</sup> week, you will work on a milestone of project 0.
The total number of weeks is 7.
Note that you cannot work on the last milestone of project 0 on 8<sup>th</sup> week because it would violate the rules.
Thus, one milestone in project 0 will remain unfinished.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>n == milestones.length</code></li>
	<li><code>1 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>1 &lt;= milestones[i] &lt;= 10<sup>9</sup></code></li>
</ul>