
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
It is known that the Morse letters $A, B, C$ are composed of two signals: dot and dash. We want to create a new alphabet using these signals with the following considerations:

a) Each letter should correspond to a sequence of seven signals;

b) If a signal in any letter is incorrectly transmitted during telecommunication, the letter should still be recognizable.

How many letters can this alphabet have?

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