
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 the radius of the Earth is $6371$ kilometers, Shanghai is located at approximately east longitude $121^{\circ}$, north latitude $31^{\circ}$, and Taipei is located at approximately east longitude $121^{\circ}$, north latitude $25^{\circ}$. The spherical distance between the two cities is approximately $\boxed{\text{answer}}$ kilometers (rounded to the nearest kilometer).

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