=begin

The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.

Find the sum of all the primes below one million.

=end

upbound = 1000000
nums = []
2.upto upbound do
  nums.push true
end
nums.each_index do |i|
  if nums[i] == true
    j = 2*i+2
    while j <= (upbound - 2)
      nums[j] = false
      j += (i+2)
    end
  end
end

sum = 0
nums.each_index do |i|
  sum += (i + 2) if nums[i]
end
print(sum)