
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Three people, A, B, and C, play a game with three cards, each displaying a positive integer $p$, $q$, and $r$, with $p < q < r$. The cards are shuffled and distributed to the three people, each receiving one card, and the number of marbles received by each person corresponds to the number on their card. After that, the cards are collected and shuffled again, but the marbles remain with the individuals. This process is repeated at least twice. It is known that at the end of the game, A, B, and C have 20, 10, and 9 marbles respectively, and B knows that he received $r$ marbles in the last round. Who received $q$ marbles in the first round?

Present the answer in LaTex format: \boxed{Your answer}
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