new_contents: #!/usr/bin/env python
  
  # returns set of natural numbers less
  # than 'less_than' and a multiple of the values in 'multiples_of'
  # e.g. less_than=10 and multiple_of=[3,5] would return [0, 3, 5, 6, 9]
  def natural_numbers_multiple(less_than=0, multiples_of=[]):
    return set([x for x in xrange(0,less_than) for m in multiples_of if x % m == 0])
  
  multiples = natural_numbers_multiple(less_than=1000, multiples_of=[3,5]);
  print sum(multiples)
subject: add solution to problem 1