n! means n 
(n 
1) ... 3 2 1
For example, 10! = 10 9 ... 3 2 1 = 3628800,
and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.
Find the sum of the digits in the number 100!
这个对于python来说实在太小儿科了。一句话的事：
print sum(int(x) for x in str(reduce(lambda x, y: x*y, range(1, 101))))