Brain-hacking calculations make Road to Olympia contestants kneel down to calculate

This is a question in the Road to Olympia program with a very high level that makes the contestants have to send a lot of money to calculate.

In the Finish Line contest of contestant Minh Hoang, a difficult calculation appeared, causing all 4 climbers to give up. The question was as follows: "A is a natural number with 2020 digits. A is divisible by 9, B is the sum of A's digits, C is the sum of B's ​​digits, D is the sum of C's digits. Find D?"

Right after the MC asked the question, contestant Minh Hoang knelt down in the middle of the stage to make it easier to calculate. The Hanoi male student gave the correct answer as 9, however the answer was incorrect. None of the remaining contestants gave an answer to this calculation.

The brain-hacking calculation made the Road to Olympia contestant kneel down to calculate.

If you find the answer to this problem, scroll down to the comments to leave a comment and see how many people think the same as you.

Source: https://vtcnews.vn/phep-tinh-hack-nao-khien-thi-sinh-duong-len-dinh-olympia-phai-quy-goi-tinh-toan-ar931104.html