To count number of quadruplets with sum = 0

[Marc 'BlackJack' Rintsch]

In <7x6491k9t3.fsf at ruckus.brouhaha.com>, Paul Rubin wrote:

> "n00m" <n00m at narod.ru> writes:
>> h = collections.defaultdict(itertools.repeat(0).next)
> 
> Something wrong with 
>    h = collections.defaultdict(int)
> ?????

According to a post by Raymond Hettinger it's faster to use that iterator
instead of `int`.

Ciao,
	Marc 'BlackJack' Rintsch