#!/usr/bin/env ruby

problem = 3
input = File.readlines("#{problem}.input").join

enabled = true
result = input
  .scan(/mul\(\d{1,3},\d{1,3}\)|do\(\)|don't\(\)/)
  .map do |cmd|
    case cmd
    when "do()"
      enabled = true; nil
    when "don't()"
      enabled = false; nil
    when /mul/
      if enabled
        cmd.scan(/(\d{1,3}),(\d{1,3})/).flatten.map(&:to_i).inject(1, :*)
      end
    end
  end.compact.sum
puts result