import sys from math import factorial def f(n): ''' gt;gt;gt; f(0) 0! is 1 There is no 3 in 1 gt;gt;gt; f(10) 10! is 3628800 There is one 3 in...

import sys

from math import factorial

def f(n):

  '''

  >>> f(0)

  0! is 1

  There is no 3 in 1

  >>> f(10)

  10! is 3628800

  There is one 3 in 3628800

  >>> f(20)

  20! is 2432902008176640000

  There is one 3 in 2432902008176640000

  >>> f(24)

  24! is 620448401733239439360000

  There are 5 3's in 620448401733239439360000

  >>> f(28)

  28! is 304888344611713860501504000000

  There are 3 3's in 304888344611713860501504000000

  >>> f(3); f(11); f(15)

  3! is 6

  There is no 3 in 6

  11! is 39916800

  There is one 3 in 39916800

  15! is 1307674368000

  There are 2 3's in 1307674368000

  '''

  if n < 0:

    sys.exit()

  n_factorial = factorial(n)

  nb_of_threes = 0

  # Insert your code here

if __name__ == '__main__':

  import doctest

  doctest.testmod()