
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 sets of consecutive integers $\{1\}$,$\{2, 3\}$,$\{4,5,6\}$, and so on, where each set contains one more element than the previous set, and the starting element is the preceding set's last number plus one. Let $S_n$ be the sum of the elements in the nth set. Determine the value of $S_{15}$.
A) 1625
B) 1695
C) 1765
D) 1855

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