
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
A and B take turns marking numbers from 1 to 17. The rules are: a number that is already marked, twice a marked number, or half a marked number cannot be marked again. The player who cannot mark a number loses. Now, A has marked 8 first. To ensure victory, what number should B mark next?

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