
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
A ball invites 2018 couples, each assigned to areas numbered $1, 2, \cdots, 2018$. The organizer specifies that at the $i$-th minute of the ball, the couple in area $s_i$ (if any) moves to area $r_i$, and the couple originally in area $r_i$ (if any) exits the ball. The relationship is given by:
$$
s_i \equiv i \pmod{2018}, \quad r_i \equiv 2i \pmod{2018},
$$
with $1 \leq s_i, r_i \leq 2018$. According to this rule, how many couples will still be dancing after $2018^2$ minutes? (Note: If $s_i = r_i$, the couple in area $s_i$ remains in the same area and does not exit the ball).

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