title: Given list of integers,remove odd positions of the list(starting from position 1(index 0) until the list contains a single element in minimum time
body: <p>I'm given a list of numbers,I need to remove the odd positions of the list  until my list contains a single number<br>
  Given list: (0,1,1,2,3,5,8,3,1)<br>
  Explanation:(1,2,5,3)<br>
              (2,3)<br>
              (3)<br>
  Answer:3<br>
  Constraint:1 ≤ No. of elements of the list ≤ 10^18</p>
  
  <p>I've tried to find the solution using slicing in loop but as the no. of elements can vary from 1 to 10^18 it will take a lot of time to complete the operation.Therefore I'm searching for an optimized solution.</p>
  
  <pre class="lang-py prettyprint-override"><code>while(len(R)&gt;1):
      R=R[1::2]
  print(R[0])
  </code></pre>
  
  <p>The output was as expected but takes a lot of time to execute when the no. of elements is increased.So searching for an optimized solution.</p>