
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
With the number written on the board, it is allowed to perform one of the following operations:
1) If the original number has a digit that is not 9, and it has two neighboring digits greater than 0, you can increase this digit by 1 and decrease the neighboring digits by 1.
2) Subtract 1 from any non-zero digit, except the last one, and add 3 to the next digit.
3) Decrease any large enough digit by 7.

If one or more leading zeros appear as a result of any of these operations, they are automatically discarded.

Initially, a number consisting of one hundred nines was written on the board. In the end, a single-digit number remained. What is that number?

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