PRINCIPAL ACCOUNTING POLICIES - Performance obligation (Details) - CNY (¥) ¥ in Millions	Mar. 31, 2022	Mar. 31, 2021
PRINCIPAL ACCOUNTING POLICIES
Transaction price allocated to remaining performance obligations	¥ 4.1	¥ 5.4

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130556-203045

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