<p>You have a list <code>arr</code> of all integers in the range <code>[1, n]</code> sorted in a strictly increasing order. Apply the following algorithm on <code>arr</code>:</p>
<ul>
<li>Starting from left to right, remove the first number and every other number afterward until you reach the end of the list.</li>
<li>Repeat the previous step again, but this time from right to left, remove the rightmost number and every other number from the remaining numbers.</li>
<li>Keep repeating the steps again, alternating left to right and right to left, until a single number remains.</li>
</ul>
<p>Given the integer <code>n</code>, return <em>the last number that remains in</em><code>arr</code>.</p>
