def random_number(seed)
  Random.new(seed).rand(2**32)
end

now = Time.now.to_i
seed = now - 123
rng_output = random_number(seed)

def crack_it(start_time, rng_output)
  seed = start_time
  loop do
    return seed if random_number(seed) == rng_output
    seed -= 1
  end
end

puts "Predictable seed: #{seed}, output: #{rng_output}"
puts "Cracked seed: #{crack_it(now, rng_output)}"