
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
On the blackboard, all natural numbers from 1 to 1988 are written. These numbers are alternately subjected to operations \( A \) and \( B \), starting with \( A \), then \( B \), then \( A \), then \( B \), and so on. Operation \( A \) is to subtract the same natural number from each number written on the blackboard (the number subtracted can be different for different \( A \) operations); operation \( B \) is to erase any two numbers on the blackboard and write their sum. The operations continue until, after a \( B \) operation, only one number remains on the blackboard. Given that this number is non-negative, find this number.

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