new_contents: #!/usr/bin/env python3
  
  from functools import *
  
  def gcd(a, b):
      assert a >= 0 and b >= 0
      if a < b:
          a, b = b, a
      while b != 0:
          a, b = b, a % b
      return a
  
  def lcm(a, b):
      return a * b // gcd(a, b)
  
  print(reduce(lcm, range(1, 21)))
  
subject: Solve problem 5