SUMMARY OF PRINCIPAL ACCOUNTING POLICIES - Intangible assets and Impairment of long-lived assets (Details) - CNY (¥) ¥ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Intangible assets
Estimated useful life	10 years
Accumulated amortization	¥ 8,632	¥ 6,985
Amortization expense	1,738	1,708	¥ 1,794
Impairment, Long-Lived Asset, Held-for-Use
Impairment recognized	¥ 0	¥ 0	¥ 0

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- References

No definition available.

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- Definition

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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- References

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