
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
Given that two points $P\_1(x\_1, y\_1)$ and $P\_2(x\_2, y\_2)$ on the curve $F(x, y) = 0$ satisfy $x\_1 \leqslant x\_2$ and $y\_1 \geqslant y\_2$, these two points are referred to as a pair of "twin points" on the curve $F(x, y) = 0$. Among the following curves:

1. $\frac{x^2}{20} + \frac{y^2}{16} = 1 (x y > 0)$;
2. $\frac{x^2}{20} - \frac{y^2}{16} = 1 (x y > 0)$;
3. $y^2 = 4x$;
4. $|x| + |y| = 1$.

Identify the sequence number(s) of the curve(s) that contain "twin points".

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