title: Python long multiplication
body: <p>I'm in need of an algorithm faster than the current normal Python long multiplication.</p>
  
  <p>I tried to find a decent Karatsuba implementation, but I can't.</p>
  
  <pre><code>def main():
      a=long(raw_input())
      if(a&lt;0):
          a=a*-1
          a=((a*(a+1)/2)-1)
          print(-a)
      else:
          a=(a*(a+1))/2
          print(a)
  main()
  </code></pre>
  
  <p>As you see, it's nothing complicated, just a few multiplications. But it has to handle numbers with up to 100000 digits in under 2.5 sec.</p>
  
  <p>I'd like some snippet of a function or just a link to some implementation of a faster multiplication function, or anything that helps.</p>