Contest: LEGO Harry Potter sets to be won

If you are a fan of LEGO and the Harry Potter universe, I don't need to remind you that the 71043 Hogwarts Castle set is now available in the LEGO Shop for members of the VIP program (of which you are obviously already part ...).

6020 pieces, a small handful of minifigs, a large ladle of micro-figurines, a retail price of € 419.99 (€ 449.99 in Belgium) and a large shelf needed to display this reproduction of Hogwarts, everything has already been said on the subject.
If you have weighed the pros and cons at length and passion outweighs logistical or financial considerations, you can checkout in the LEGO Shop directly via the links below depending on your country of residence:

In addition to this availability and to mark the occasion, I suggest you try to win one of the four boxes generously offered by LEGO, the sets 75954 Hogwarts Great Hall, 75956 Quidditch Match, 75953 Hogwarts Whomping Willow et 41621 Ron Weasley & Albus Dumbledore, by participating in the small contest below.

As usual, I'm asking you a question (which I couldn't choose this time), it's up to you to find the answer. Four winners will be drawn from among the correct answers.

The email addresses and other personal data collected during this competition will NOT be used for any purpose other than checking the validity of entries and the drawing of lots, they never are. No participation via comments.

Good luck to everyone.

to Rafflecopter giveaway