# 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.
def answer
  (1..999).reduce(0) do |result, number|
    result += number if number % 3 == 0 || number % 5 == 0
    result
  end
end

puts answer()
