
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
Consider the sequence $\{5, 55, 555, 5555, \ldots, 555555555\}$ consisting of nine numbers where each number is composed of digits that are all 5s, and the number of 5s increases by one in each subsequent number. Calculate the arithmetic mean, $N$, of these numbers, a 9-digit integer. Identify which digit from 1 to 9 does not appear in $N$.
A) 1
B) 3
C) 7
D) 0
E) 2

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