Number of zeroes in factorial of a number

Write a function that returns the number of zeros contained in the factorial of the number that is passed to it.

Ok, so the easy solution is to calculate factorial and then count the nb of zeroes. But we cannot have very large number.
Our solution is to divide the number as we compute it by ten when it's possible and increment the counter:

count = 0
def zeroes(n):
        global count
        if n == 1:
                return 1
        else:
                v = n * zeroes(n-1)
                if v % 10 == 0:
                        print v
                        v /= 10
                        count += 1
                return v

print zeroes (100)
print count

import math
print math.factorial(100)