LEASES - Supplemental components of cash flow (Details)	3 Months Ended
	Jul. 31, 2019 USD ($)
LEASES
Operating cash flows from operating leases	$ 112,000
Financing cash flows from finance leases	16,000
Total cash paid for amounts included in the measurement of leases	$ 128,000
Weighted average remaining lease term, operating leases	7 years 2 months 27 days
Weighted average remaining lease term, finance leases	1 year 1 month 13 days
Weighted average discount rate, operating leases	4.51%
Weighted average discount rate, finance leases	5.45%