
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 are written the numbers $1, 2, 3, \cdots, 1986, 1987$. In each step, some of the written numbers are erased and replaced by the remainder of their sum when divided by 7. After several steps, two numbers remain on the blackboard, one of which is 987. What is the other remaining number?

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