# number is an empty array
number = []
# the for loop will use variable 1 to separate each number between 1 and 999
for i in 1..999 do
  # each number that is divisible by 3 or 5 will be pushed into array number
  number << i if i % 3 == 0 || i % 5 == 0

end
  # .reduce is adding the elements of number together
puts number.reduce(:+)