How to enter the Vienna Opera House to watch an opera at the cheapest price on the same day?

When I planned to go to Vienna, I found that all the operas were sold out, with only very expensive tickets left. But an opera lasts about 4 hours, and I don’t want to buy standing tickets and spend that much time. Fortunately, the opera house now offers tickets for seats with obstructed views every morning, and they are only 15 euros! It is cheaper than the student ticket which is 20 Euros. Although the view is blocked, the overall viewing experience is still very good! #Vienna State Opera