
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 $7 \times 7$ board is either empty or contains an invisible $2 \times 2$ ship placed "on the cells." Detectors can be placed on certain cells of the board and then activated simultaneously. An activated detector signals if its cell is occupied by the ship. What is the minimum number of detectors needed to guarantee determining whether the ship is on the board and, if so, identifying the cells it occupies?

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