title: maximum of gcd of huge list of number
body: <p>I need a very very fast python algorithm that can find max of gcd of 100,000 numbers in shortest time!</p>
  
  <p>and here is my code but it's too slow for huge lists.</p>
  
  <pre><code>for x in mlist:
      for y in mlist[i:]:
          tmp = gcd(x, y)
          if tmp &gt; highest:
              highest = tmp
      i += 1
  print(highest)
  </code></pre>
  
  <p>thank you</p>