
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
Fill in the numbers $1$ to $9$ into a $3\times 3$ grid so that the sum of numbers in each row, each column, and both diagonals are equal. This forms a "magic square," originating from the ancient Chinese "Lo Shu" square, which is the earliest known magic square in the world. In the partially filled "magic square" shown below, the value of $a-b$ is ______.

| 8 |   |   |
|---|---|---|
|   | 5 | a |
| b |   |   |

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