''' 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! '''

a = 1
sum = 0
for i in xrange(1, 101):
  a *= i
while a > 0:
  sum += a % 10
  a /= 10
print sum