sum : Int64 = 0
part1 : Int64 = 0
part2 : Int64 = 0
done1 = false
done2 = false

spawn do
  (0..500000000).each do |num|
    part1 += num
  end
  done1 = true
end

spawn do
  (500000001..1000000000).each do |num|
    part2 += num
  end
  done2 = true
end

while !done1 && !done2
  sleep 1.second
end

sum = part1 + part2