This problem should be good for the English among you-

There is an amazing concert that's just been announced that you want to go to, there are 500 tickets and the tickets will be going on sale at noon. It's an online checkout, so there are 500 checkout sessions available to start selling tickets at noon, but there is only a single queue to feed all 500 checkouts. There are 20,000 real people that all want to buy tickets including you.

There's a catch however- once you are through the queue and in a checkout session, you have 30 minutes to complete checkout. After 30 minutes you will be booted and have to re-enter the queue. Let's say half of the people are aware of this rule and half are unaware and think they can just queue up really early and be safe.

You are able to tell how many people are ahead of you in the queue and generally the pace at which the queue is moving, but you can't tell how many people are behind you because the website locks you to just one browsing session, and you can't have someone else coordinate to buy the tickets for you because they have a name and require ID.

Your possible actions are:
-Enter the Queue
-Leave the Queue
-Continue to wait in the Queue

So the question is what time do you enter the queue to make sure you are in a checkout session with less than 30 minutes until noon?