gistfile1.rb

class Integer
  def factorial_iterative  
    f = 1; for i in 1..self; f *= i; end; f    
  end

  def sum_digits
    self.to_s.split(//).collect { |d| d.to_i}.sum
  end
end

### Bruteforce!
(1..1000).each do |cur|
  puts cur and break if cur.factorial.sum_digits == 8001  
end