
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
How many positive integers  $A$  are there such that if we append  $3$  digits to the rightmost of decimal representation of  $A$ , we will get a number equal to  $1+2+\cdots + A$ ? $ 
\textbf{a)}\ 0
\qquad\textbf{b)}\ 1
\qquad\textbf{c)}\ 2
\qquad\textbf{d)}\ 2002
\qquad\textbf{e)}\ \text{None of above}
$ 

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