
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
Murtha has decided to expand her pebble collection. She already has 3 pebbles to start with. On the first day, she collects two pebbles and on the second day, she collects three pebbles. On each subsequent day, she collects one more pebble than the previous day. How many pebbles will she have collected at the end of the fifteenth day?

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