SHARE-BASED COMPENSATION (Details)	12 Months Ended
Dec. 31, 2020 CNY (¥) shares	Jan. 01, 2019 $ / shares
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized	61,605,996
Options expire term	10 years
2015 Plan \| Employee options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense \| ¥	¥ 131,344
2015 Plan \| Non-employee options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	4 years
Stock-based compensation expense \| ¥	¥ 34,285
Share options granted	4,936,000
Fair value of the ordinary share (per share) \| $ / shares		$ 2.26
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized	45,765,386
Options expire term	10 years
2015 Plan and 2020 Plan \| Employee options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	4 years

Represents the fair value of common stock on repurchase date.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Number of shares authorized for issuance under share-based payment arrangement.

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Gross number of share options (or share units) granted during the period.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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