
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 ancient Greek mathematicians associated natural numbers with polygons as follows:
Triangular numbers: $1,3,6,10,15$, 
Square numbers: $1,4,9,16,25$, 
Pentagonal numbers: $1,5,12,22,35$, 
Hexagonal numbers: $1,6,15,28,45$

According to the above sequence, the 8th triangular number is $\qquad$.

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