
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 pattern in the following "number array":  
10, 11  
20, 21, 22  
    ...  
90, 91, 92, ..., 99  
100, 101, ..., 109, 1010  
    ...  
990, 991, ..., 999, 9910, ..., 9999  
1000, ..., 1099, 10010, ..., 10099, 100100  
    ...  
2000, ..., 2009, 20010, ..., 20099, 200100, ..., 200200  
Then, the number 1991 appears in the $\boxed{\text{nth row}}$ and the $\boxed{\text{mth position}}$ of that row. It is also the $\boxed{\text{kth number}}$ in the entire number array (counting from the beginning).

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