
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
A boy wrote the first twenty natural numbers on a piece of paper. He didn't like how one of them was written, so he crossed it out. Among the remaining 19 numbers, there is one number that equals the arithmetic mean of these 19 numbers. Which number did he cross out? If the problem has more than one solution, write down the sum of these numbers.

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