
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
The units digit of a positive integer \( m \) is denoted by \( f(m) \). Define \( a_{n}=f\left(2^{n+1}-1\right) \) for \( n = 1, 2, \ldots \). What is \( a_{1994} \)?

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