
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 positioned exactly on the cells of the board. It is allowed to place detectors in some cells of the board and then activate them simultaneously. An activated detector signals if its cell is occupied by the ship. What is the minimum number of detectors needed to ensure, based on their readings, whether the ship is on the board, and if so, to determine which cells it occupies?

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