new_contents: from operator import mul
  from fractions import Fraction
  
  def nCk(n,k): 
      return int(reduce(mul, (Fraction(n-i, i+1) for i in range(k)), 1))
  
  def nPk(n, k):
      return int(reduce(mul, (n - i for i in range(k)), 1))
  
  if __name__ == "__main__":
      L = 16
      ans = 0
      for i in range(3, L + 1):
          ans += 15 * 16 ** (i - 1) + 41 * 14 ** (i - 1) - (43 * 15 ** (i - 1) + 13 ** i)
      print '%X' % ans
  
subject: add 162