
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
Given the operation defined as $1 ※ 2=1+2=3, 2 ※ 3=2+3+4=9, 5 ※ 4=5+6+7+8=26$, if $a ※ 15=165$, then find the value of $a$.

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