
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
Observe the following number array, it is easy to see that the number on the far right of the $n$th row is $n^2$. Then, the number on the far left of the 20th row is ____.

1  
2   3   4  
5   6   7   8   9  
10 11  12  13  14  15  16  
17 18  19  20  21  22  23  24  25  
…

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