
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
The function \( f(x,y) \) satisfies the following conditions: 
1. \( f(0,y) = y + 1 \)
2. \( f(x+1,0) = f(x,1) \)
3. \( f(x+1,y+1) = f(x,f(x+1,y)) \)

for all non-negative integers \( x \) and \( y \). Find \( f(4, 1981) \).

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