
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
Students A, B, C, D, and E plan to borrow books from four categories, labeled $A$, $B$, $C$, and $D$, in the school library (each category contains several books). It is known that each student will only borrow one book, each category of books will be borrowed, and student A will only borrow books from category $A$. The number of different borrowing schemes is \_\_\_\_\_\_ (Answer in digits).

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