INCOME TAX EXPENSES - Movement of valuation allowance (Details) - Valuation Allowance of Deferred Tax Assets - CNY (¥) ¥ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Movement of valuation allowance
Balance at beginning of the year	¥ 31,852	¥ 20,358	¥ 11,379
Provided	8,180	11,494	8,979
Balance at end of the year	¥ 40,032	¥ 31,852	¥ 20,358

Amount of valuation and qualifying accounts and reserves.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column E))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-4

Name:	us-gaap_ValuationAllowancesAndReservesBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant