
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
Given the pseudocode below, if the algorithm is intended to compute the result of $-1 + 3 - 5 + 7 - 9$, what should be the initial value of $a$, denoted as $x = \_\_\_\_\_\_\_$.

```
S ← 0
a ← x
For I From 1 To 9 Step 2
    S ← S + a × I
    a ← a × (－1)
End For
Print S
```

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