title: Time to merge sorted lists into single sorted list?
body: <p>Given <code>logN</code> sorted lists each of size <code>N*logN</code>. What is the total time required to merge them into single sorted list?</p>
  
  <pre><code>A) O(NlogN)
  B) O(N)
  C) O(NloglogN)
  D) O(Nlog(N/logN))
  </code></pre>
  
  <p>I tried solving it by taking N=4. But no option is satisfying.</p>