# If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
# Find the sum of all the multiples of 3 or 5 below 1000.

sum = 0
1.upto 999 do |n|
  i = 0
  n.to_s.each{|d| i += d.to_i}
  if (['0','5'].include?(n.to_s[n.to_s.length - 1,1]) || i % 3 == 0)
    sum += n
  end
end
print sum